
Class JOLiZTi 

Book Ed 

finyiMifH / ■? ..: 4 



COPYRIGHT DEPOSED 



EXPERIMENTAL 
WIRELESS STATIONS 

Their Theory, 
Design, Construction and Operation 



INCLUDING 






WIRELESS TELEPHONY, VACUUM TUBE AND QUENCHED 


SPARK 


SYSTEMS. A COMPLETE ELEMENTARY COURSE 


OF 




INSTRUCTION IN AND AN ACCOUNT OF SHARPLY 






TUNED MODERN WIRELESS INSTALLATIONS 






By 






PHILIP E. EDELMAN, E.E. 






Author of "Inventions and Patents," "Experiments," Etc. 






Sill 






NEW. 19gg EDITION 






A NEW BOOK FROM COVER TO COVER WITH ENTIRELY NEW 


EN- 


GRAVINGS. REVISED, ENLARGED AND RESET EDITION, 




SHOWING ALL RECENT IMPROVEMENTS 






FULLY ILLUSTRATED 







NEW YORK 


THE NORMAN W. HENLEY PUBLISHING COMPANY 


2 WEST 45th STREET 


1922 



,^r 






U 



Copyright, 1920 akd 1922 by 

THE NORMAN W. HENLEY PUBLISHING COMPANY 



Copyright, 1912, 1914, by 
PHILIP E. EDELMAN 



ALL RIGHTS RESERVED 



PRINTED IN U. S. A. 



# 



/ 



All illustrations in this book have been specially made by the 
publishers, and their use without permission is strictly prohibited 



MAY 131922 
©P..A661644 



PREFACE TO THE 1922 REVISED AND 
ENLARGED EDITION 

During the recent World War, the earlier editions 
of this book were extensively used in the United 
States and Allied Training Camps, and were found to 
be readily understandable text for beginners in the 
art of Wireless Communication, who wished to start 
with the elements and continue thoroughly. 

The readers of this book are assumed to have some 
knowledge of the fundamentals of electricity and mathe- 
matics. The knowledge of these branches need not 
be very extensive but when they have finished this 
book they will find themselves well advanced in the 
study of a fascinating subject. From the standpoint 
of operation, the best modern practice is presented in 
such simple language as to be well within the scope 
of the average reader. The basic principles of radio- 
communication, involving the theory and mathematics 
of the subject, are given in considerable detail, so that 
they can be followed consecutively by the reader. 
There is plenty of room in radio work for the exercise 
of individual ingenuity, and this book will enable the 
reader, while exercising such ingenuity, to reach re- 
sults without depressing failure. 

There is an army of wireless operators in all parts 
of this country, many of which figure as amateurs. 

iii 



iv Preface 

Many of them are so expert as to be ranked with pro- 
fessional operators. A standard design for so-called 
"Amateur Stations" will be found in this book, and 
this design is for a thoroughly practical working plant. 
Although many of the younger workers in this branch 
are still in the elementary stage, the study of such a 
work as the present one, combined with the practice 
they are daily receiving in their own laboratories and 
stations, will convert them rapidly into operators 
qualified for serious work in the commercial field. 

The science of radio communication is developing 
with astonishing rapidity. One detector after an- 
other has gone out of use, as something better has 
been developed. The vacuum-tube rectifier has 
changed the whole aspect of the science and promises 
to have a permanent position. There are, however, 
any quantity of advances in details yet to be made, 
and the most recent of these in vacuum tube circuits, 
radio-telephony, mitigation of interference and general 
improvements are presented in this edition. 

Radio communication played so important a part 
in the recent war that it puts the amateur operator in 
the position of a volunteer in training for patriotic 
service. There is so much to be done in the future 
that students of the art may feel that their life work 
is laid out for them in this fascinating study. 

Suggestions from the readers will be most welcome. 

The Author. 
March, 1922. 



- List of Symbols - 



I" '" or "' y or " "Y 



Antenna 

Ground ----» __L. 

— or I 



Wire Connections : 



No Connections r of Wires 



\ 




Fixed Resistance — WWV— 

Variable Resistance -WWV or --- — vna^vv— 

-_^^_ 

-©- — - -^- 

/volts 

-©- ......... -0L 

/amperes 

_0_ ......... _0l 

/GALVO. 

CrK5/<7/ Detector ■ >^ 



Vacuum Tube 



Telephone Receivers - 
Voltmeter- 

VOLTS 

Ammeter 

Galvanometer 

'gaTvo 



-List of Symbols - 

Battery - "^|l|l|lr" 

Direct Current Dynamo --- m. Q ^ or 



Alternating 

Current 

Generator 



Fixed Capacitance 
(Condenser ) 



} -0- -■ -JQT 




Variable Capacitance 1 U* 

(Var. Condenser) /|| 

Fixed Inductance ••xx-a-xa-an 

(AirCoreCoil) WWWU 



*^c£c%r -ntpfo- or -rw^ 



Variometer (Variable Inductance) — 



Fixed Coupling of Coils ____ -\£flflflJL/-- 

(Fixed Inductive Coupling) / "ft"A7ffT N 

-..- JO/— 

Variable Coupling of Coils 



Transformer— 

Iron Core Inductance 
( or Reactance Coil) 




-^SflWV 



CONTENTS 

CHAPTER I 
NATURE OF WIRELESS TRANSMISSION 

PAGE 

Theory; Action of Radiant Waves; Interference; How 

Signals Are Sent; Wave Lengths Used 11 

CHAPTER II 

AERIALS 

The Antenna; Dimensions; Supports; Height and Length; 
Various Types ; 200 Meter Design ; Table for Various 
Wave Lengths ; Radiation Resistance ; Capacity and 
Inductance; Insulation and Construction.; Poles and 
Guy Wires 23 

CHAPTER III 

COIL AND SUB-SURFACE SYSTEMS 

Multi-Turn Coil Receiver; Portable Receiving Long Dis- 
tance Set; Principle of Coil Action; Directional Effects 
of Coils ; Types and Construction ; Radio Compass. 
Sub-Surface Radio; Antenna Buried Underground; 
Roger's System; U. S. Navy Experiments .... 48 

CHAPTER IV 

GROUNDS AND LIGHTNING PROTECTION 

Ground Connections ; Various Types ; Construction ; Light- 
ning Protectors ; A Safe Radio Station ; Underwriter's 
Rules 57 



vi Contents 

CHAPTER V 

THE TRANSMITTER AND RESONANCE 

Transmitting Circuit; Principle of Oscillations; Action of 
Energy; Resonance; Period of Vibration; Adjustments; 
Harmonic Effects ; Resistance ; Beats ; Typical Curves 
for Various Transmitters; Damping; Relation of An- 
tenna Current and Voltage; Experiment Illustrating 
Coupling 65 

CHAPTER VI 

WAVE LENGTH, CAPACITY, AND OSCILLATION 
CIRCUITS 

Damped Wave Transmitter; Calculation of Wave Length, 
Capacity, and Circuits ; Range of Transmission ; Power ; 
Frequency and Voltage ; Table of Capacities ; Formula 
for 200 Meter Calculations ; Spark Gap ; Antenna Cir- 
cuit; Percentage of Coupling; Example of a Complete 
Spark Transmitter; Dimensions 90 

CHAPTER VII 

TRANSFORMERS AND SPARK COILS CONSTRUCTION 
DETAILS 

Principle of Induction Coil; Transformer Construction 
Data; Building a Transformer; Reactance Coil; Spark 
Coil ; Table for Various Spark Coils with Dimensions 108 

CHAPTER VIII 

AUXILIARY APPARATUS 

Keys ; Electrolytic Interrupter ; Kickback Prevention ; Aerial 
Switches; Automatic Antenna Switch; Storage Bat- 
teries ; . . . 121 

CHAPTER IX 

CONDENSERS AND CAPACITIES 

Condenser Theory; Calculation of Capacities; Dielectric 
Table; Building Condensers; Dimensions and Mate- 
rials 133 



Contents vii 

CHAPTER X 

INDUCTANCES 

Calculation of Inductance; Construction of Helix and Os- 
cillation Transformer; Simple Formulas for Definite 
Low Wave Length Sets 148 

CHAPTER XI 

' SPARK GAPS 

Purpose of Gap; Materials Suitable; Series Gap; Rotary- 
Gap; Construction of Rotary Gapj Rotary Quenched 
Gap ; Rotary Gap Circuits ; Chaffee Gap ; Two Tone 
Gap 158 

CHAPTER XII 

RADIATION INDICATORS AND MEASUREMENTS 

Use of Radiation Indicators ; Hot Wire Ammeter Construc- 
tion; Wave Meter; Use of Hot Wire Ammeter; Shunt 
Resonator ; Cost of Transmitter Complete ; Frequency ; 
Decrement ; Logarithmic Decrement Illustrated ; Elec- 
tron Tubes for Measurements ; Audion Connected to 
Wave Meter 170 

CHAPTER XIII 

ADVANCED SYSTEMS 

Continuous Waves; Wireless Telephone; Quenched Spark; 
High Frequency Alternators ; Demonstration of Arc 
Radiotelephone ; Poulsen Arc ; Construction of 
Quenched Gap ; Lepel Gap ; Advantage of Quenched 
Gaps ; Wireless Piano ; Goldschmidt Alternator ; Alex- 
anderson Alternator ; Magnetic Modulator ; Static 
Transformer Frequency Multiplier ; Onde Unique Sys- 
tem ; Vacuum Tube Methods ; Duplex High Speed 
Operation; Wave Changing Systems 187 

CHAPTER XIV 

VACUUM VALVES AND CIRCUITS 

Vacuum Tubes ; Amplifiers ; Detectors ; Oscillators ; Modu- 
lators ; Tube Radiotelephones ; Experiments Showing 



viii Contents 

Fundamental Action ; Two and Three Electrode Tubes ; 
Curves of Operation; How the Circuits Work; Opera- 
tion of Grid ; Audion Circuits ; Lieben Reisz Amplifier ; 
Pliotron ; Cascade Amplifier ; Outside Grid Tube ; Dyna- 
tron ; Chart of Vacuum Tube Circuits for all Purposes ; 
Ultra-audion Receiver ; Damped and Undamped Wave 
Circuits ; Audion Generator ; Armstrong Circuit ; Con- 
struction of Long Wave Length Oscillating Receiver; 
Adjustment of Oscillating Circuit; Short Wave Length 
Repeating Amplifying Receiver ; Cascade Circuits ; Ad- 
vantages and Disadvantages of Audion ; Combined Crys- 
tal Detector and Audion ; Sensitizing Circuits ; Special 
Vacuum Tube Circuits; Self-tuned Oscillation Genera- 
tor; Self-Modulated Transmitter; New Tube Circuits 207 

CHAPTER XV 

TUBE RADIOTELEPHONES 

Modulation Systems; Portable Radiotelephone; Transconti- 
nental Wireless Telephone ; Connection of Tubes ; U. S. 
Army Set; U. S. Navy Set; A Wireless Telephone 
Operated from Your Lamp Socket ; Power Tube Radio- 
telephone ; A Small Amateur Radiophone ; Cost of a 
Telephone Set 238 

CHAPTER XVI 

THE RECEIVING STATION 

Operation of Receiver; Telephone Receivers; Purpose of 
Detector; Energy of Signal Received; Types of De- 
tectors ; Principles of Operation 251 

CHAPTER XVII 

DETECTORS 

Vacuum Tube Detectors; Solid Rectifiers; Crystals; Con- 
struction of Detectors; Crystal Mounting; Adjust- 
ments; Buzzer Test 257 

CHAPTER XVIII 

SENSITIVE INDICATORS FOR RECEIVING SETS 

Telephone Receivers; Continuous Wave Detectors; Ein- 
thoven Galvanometer; Construction of Indicators; 
Automatic Indicators; Hoxie Photographic Recorder; 



Contents 



IX 



Amplifiers ; Microphone Amplifier ; Baldwin Receiver ; 
Adjustments; How Receiver Operates; Measuring In- 
tensity of Received Signal; Audibility Meter . . . 269 

CHAPTER XIX 

TUNING AND INTERFERENCE PREVENTION 

Principle of Resonance Used in Tuning; Interference; 
Mitigating Various Kinds of Interference ; Tuning 
Methods ; How to Tune a Receiving Set ; Receiving 
Circuits ; loose Coupled, Bridge, and Interference Miti- 
gating Circuits ; How to Use a Loose Coupler ; Bal- 
ancing Out Power Line Hum 283 

CHAPTER XX 

SPECIAL RECEIVING SETS 

Time Signal Receiver ; Weagant's Stray Mitigator ; Alexan- 
derson Barrage Receiver; Heterodyne Receiver; Action 
of Heterodyne Circuit ; Phase Modified Receivers ; Bal- 
ance Systems ; Construction of Phase Rotator ; Phase 
Shifting Explained; Multiple Unit Phase Shifting Re- 
ceivers ; Uni-Control and Automatic Receivers ; Ca- 
pacity Coupling ; Universal Receiving Set for Long and 
Short Damped and Undamped Wave Signals ; Autodyne 
Receiver; Magnetic Tube Sensitizer; Short Wave Os- 
cillating Receiver; New Circuits 300 

CHAPTER XXI 

RECEIVING CONDENSERS 

Construction of Fixed and Variable Condensers ; Circuits 
for Condensers ; Building a Condenser ; Korda Air Con- 
denser; Assembly of Plates; Geared Fine Adjustment 
Condenser 314 

CHAPTER XXII 

CONSTRUCTION OF RECEIVING INDUCTANCES 

Tuners ; Loose Couplers ; Loading Coils ; Sliders ; Windings 
for Desired Wave Lengths ; Variometer ; Variometer 
Phase Rotator; Switching; Dead End Elimination; Tens 
and Units Connection ; Multilayer Coils ; Compact Long 



x Contents . 

Wave Length Coils ; Couplers for Long Wave Lengths ; 
Dimensions for Various Wave Lengths ; Plural Receiv- 
ing Sets 325 

CHAPTER XXIII 

MAKING THE WIRELESS SET WORK 

Trouble Finding; Principle Faults Found; How to Make 
Repairs ; Reasons for Various Failures ; Improving Poor 
Signals 346 

CHAPTER XXIV 

MISCELLANEOUS APPLICATIONS 

Railroad Wireless ; Forest Fire Prevention ; Automobile 
Wireless ; Aeroplane Sets ; Wireless Compass ; Bellini 
Tosi Apparatus ; Multiple and Ground Aerials ; Balanc- 
ing Aerials ; Telemechanics 350 

CHAPTER XXV 

TIME AND WEATHER SIGNALS 

How Signals Are Transmitted and How to Receive Them; 
Naval Stations Sending Information; Codes Used; Ex- 
ample of Deciphered Code 357 

CHAPTER XXVI 

RADIOCOMMUNICATION4PATENTS 

A List of Patents for System and Apparatus ; Discussion of 

Some Patents , . 362 

CHAPTER XXVII 

RIGHTS OF THE EXPERIMENTER 

Information on Complete Sets ; List of Radio Stations ; The 
Law of 1912; How to Get Licenses; Radio Inspectors; 
Rules for Operating ; Patents ; Tendency of Art ; Wire- 
less Codes; Conclusion 373 



CHAPTER I 
Nature of Wireless Transmission 

Theory; Action of Radiant Waves; Interference; How sig- 
nals are sent; Wave Lengths Used. 



Before beginning the details of equipment, a brief 
outline of the essential theories which aid in under- 
standing the art will be given. To begin with, it 
should be understood that many of the elementary 
theories have only been partially substantiated and 
that in any case they serve more for convenience than 
as scientific fact. It should also be remembered^ that 





Fig. 1.— Example of a Radio System, A- A 1 , Aerials. C-C 1 , Con- 
densers. T, Transformer Coil. D, Detector. I-H, Induct- 
ances. S, Spark Gap. G, Ground. R, Telephone Receiver. 

while lines of force and similar terms are used as 
though the lines were visible and a matter of fact, they 
are merely imaginary and used for convenience. 

11 



12 Experimental Wireless Stations 

In the practical wireless station with which we are 
concerned, electromagnetic waves are utilized to trans- 
mit intelligence without the use of a conductor or 
wire between the transmitting and receiving stations. 
It has been found that these electromagnetic waves 
closely resemble light waves and for this reason some 
knowledge of the physics of light will be useful and 
an aid in the mastery of the wireless art. 

In Fig. i a simple diagram of the relations of the 
stations is shown as an example. Briefly, electromag- 
netic waves are generated by means of a discharge 
through a suitable gap which sets up oscillations in a 
shunt circuit of capacity and inductance and these 
oscillations are in turn radiated from the aerial in wave 
trains representing the dots and dashes of the code. 




Fig. 2. — Illustrating Theory of Action of Radiating Waves. 

By referring to the figure it will be observed that the 
sending and the receiving station are connected 
through the earth and that they have a second circuit 
through the space between their respective aerial ca- 
pacities. It has not been established whether the 



Theory of Wireless Stations 



13 



ground acts as the return circuit or whether the space 
serves for this purpose, but experiments have shown 
that a considerable part of the efficiency of transmis- 
sion is dependent on having good ground connections 
through soil, which is a comparatively good conduc- 
tor. In fact, the variable conductivity over different 
portions of the earth materially affects the range and 
clearness of transmission, ranging from maximum 
over water, to a minimum over dry uneven expanses 
of land. The earth is an imperfect and variable con- 
ductor in itself and it is for this reason that transmis- 
sion over different portions of the earth's surface 
varies considerably. It has not been established 




Fig. 3. — Illustrating Condenser Theory of Propagation. 

whether or not the curvature of the earth materially 
affects transmission, but it is not likely that it does. 
Good earth connections then are essential to efficient 
wireless transmission. An exceptional case in which 
no ground is required is discussed in Chapter III. 

Some experts consider that radio waves are prin- 
cipally progagated through the earth itself. 

A commonly accepted theory of the action of wire- 



14 



Experimental Wireless Stations 



less waves is illustrated in Fig. 2. The aerial (A) is 
represented by the upper part of a spark gap and the 
lower part terminates in a ground E. The aerial be- 
comes charged and sets up a field of force, the area 
of which depends on the intensity of the charge and 
other natural conditions. The lines of electrical strain 
are represented by the dotted lines and should be 
understood as of spherical form, although shown as 
in a plane on the paper. Now after the charge accum- 
ulates to a certain point, a spark passes between the 
gap electrodes, making the gap a temporary conduc- 



s ^ \ \ v v — / / > f J 



T 



Strata 



WWW //// 



\V\\W if//// \\WM '//'// 

^\\ \ » \ • " / fa ^ \ \ \ > ' ' / '/, 



u 



Fig. 4. — Heaviside Layer Theory. 



tor. The aerial discharges at this point and as a 
result the strain in the electrostatic field is relieved. 
However, a new current is simultaneously produced 
which charges the aerial in substantially the opposite 
polarity to that of the first charge, and the process is 
repeated very rapidly a number of times. That is, the 
aerial is said to oscillate or vibrate. Now, each re- 
versal of the polarity of the charge causes the direc- 
tion of the strain to change so that the lines resulting 



Wave Propagation 15 

from the first charge are displaced by lines running 
in the opposite direction, thus forming partial loops. 
These loops form a circular series of ripples or waves 
about the aerial and travel away from it at the rate 
of 300,000,000 meters per second (186,000 miles per 
second), or the speed of light. In the figure, the ar- 
rows represent the direction of the lines of strain and 
a little study of this imaginary diagram will aid in the 
understanding of wireless phenomena. It is under- 
stood, of course, that the gap is charged by a suitable 
condenser and source of power, which are not shown. 

Two complete oscillations are represented by the 
loops of Fig. 2, and the aerial is ready for a third dis- 
charge. These oscillations really occur at an exceed- 
ingly rapid rate. 

A similar argument holds in the case of a vacuum 
tube transmitter. An ever-expanding volume wave of 
electromagnetic lines of force threaded at right angles 
thereto by electrostatic tubes of force is emitted from 
the transmitter and reaches the receiver where, in cut- 
ting conductors thereof, corresponding feeble currents 
of electricity are set up in the receiving circuits. 

The function of the aerial capacities of the stations 
will be best understood, perhaps, when they are 
likened to a simple condenser. (See Fig. 3.) If this 
theory is accepted, a wireless circuit is practically a 
closed circuit in which one branch takes the form of 
a condenser. However, since the distance between 
the two aerials concerned is generally many miles, it 
is not unlikely that the effect is similar to that indi- 
cated by Fig. 4, since it has been established that the 



16 Experimental Wireless Stations 

upper strata of the atmosphere and the surrounding 
space form practically a perfect conductor. At any 
rate, the distance to which transmission may be car- 
ried out is less with relatively low aerials than with 
high ones, the other conditions remaining the same, 
and for this reason the higher the transmitting aerial 
can be supported, the better. The item of cost is the 
practical limit, however, since after a moderate height 
is reached the expense increases in a proportion many 
times greater than the corresponding increase in 
height. High antennas are unnecessary for receiving 
stations. In fact, the height of experimental aerials 
will naturally be limited for this reason and even in 
the few large commercial stations, the aerial supports 
form one of the largest items of expense. Large com- 
mercial and naval stations have supports for trans- 
mitting aerials ioo to 1,000 feet high above the earth's 
surface. 

Now the transmitted wave impulses do not travel 
only in the desired direction to the receiving station, 
but spread out in all directions with practically equal 
force. The direction of transmission can be regulated 
to some extent, however, by means of directive aerials 
which tend to make the range of transmission greater 
in one desired direction than in other directions. 
Wireless transmission is perhaps best understood by 
a comparison to the waves which result when a small 
stone is thrown into a smooth body of water. It is 
suggested that the reader try the experiment when the 
opportunity is presented, if he has not already done 
so. The stone thrown into the water corresponds to 



Wave Lengths 17 

the wave generator at the transmitting station in wire- 
less telegraphy, the water to the space or ether and the 
ripples to the electromagnetic waves. It should be 
observed that the ripples spread out continually in the 
form of a circle and that they gradually become feebler 
and feebler, until they are no longer visible. Wireless 
transmission presents a similar property and the elec- 
tromagnetic waves become feebler so that the ampli- 
tude is approximately inversely proportional to the 
distance from the sending station.* Another factor 
which limits the transmitter's effective range is the 
item of absorption. Now, it has been found that the 
absorption varies in some cases with the wave length 
employed. In general, long wave lengths are sub- 
jected to less absorption than wave lengths which are 
relatively short. Inasmuch as the experimenter is ex- 
pected to confine his experiments to the use of short 
wave lengths this is a matter of some importance. For 
example, waves having a length greater than 3,000 
meters will even penetrate several feet below the sur- 
face of the earth. In transmission over water short 
wave lengths are nearly as good as the long ones, but 
over ordinary land, long wave lengths are a material 
advantage. However, in the case of land transmission 
over dry soil, neither long nor short wave lengths ap- 
pear to have an advantage. It is understood that short 
waves mean those having a wave length of 200 meters 
or less, while long waves refer to waves having from 
1,200 to 14,000 or more meters for their wave length. 
Wave lengths between 300 and 6,000 meters are gen- 

♦This is not a rigid rule or even exact. 



18 Experimental Wireless Stations 

erally recognized as the most advantageous for ordi- 
nary purposes. 

Wave lengths as high as 30,000 meters have been 
used for transoceanic communication and 6,000 to 
15,000 meters are commonly in use by several of the 
largest stations. 

Other items which affect the transmission are ir- 
regularities in the composition of the earth such as 
mountains, minerals, etc., and daylight. It has been 
found that messages can be received over much greater 
distances at night than during the daytime. The dif- 
ference is not marked or important over short dis- 
tances and can be overcome to a considerable extent 
over long distances, by the use of long wave lengths. 
The reason why daylight affects the transmission is 
not really understood at the present time, although 
there are several theories. It is believed that the effect 
is due either to the ionization of the air or the upper 
strata or both, by the sun's light. When the theory 
that the aerial capacities of the stations form a con- 
denser is used and it is remembered that the action of 
a condenser depends largely upon having a good 
dielectric material so that there will be little leakage, 
this theory seems plausible. Rain and damp weather 
have a similar effect on transmission because the 
dielectric is presumably rendered less conductive to 
the waves and more conductive to leakage. The hu- 
midity is related therewith in that stray disturbances 
increase when the humidity increases and vice-versa. 

Now since the waves tend to spread out in every 
direction, it will be evident that all the receiving sta- 



Interfering Waves 19 

tions within the range of a transmitting station will 
be capable of receiving the same message equally well, 
other conditions remaining the same. This lack of 
secrecy is a considerable detriment to the advance of 
the art and efforts are constantly being made to over- 
come this lack of direct communication in a desired 
straight line. Instruments and apparatus have been 
developed which make it possible to either receive or 
not receive a given message with a certain degree of 
precision and directive methods have been developed 
to a certain degree as has already been mentioned. 
Another serious drawback to the advancement of the 
art is the matter of interference. This is an item which 
directly concerns the experimenter and although sev- 
eral arrangements to overcome this objectionable fea- 
ture have been developed, there is considerable room 
for improvements. 

Interference can be understood by reference to the 
experiment of throwing the stone into the water. # If 
two stones instead of one are thrown into the water, 
and if one is considerably larger than the other, it will 
be noticed that the ripples or waves from the larger 
stone tend to absorb and superpose those of the 
smaller stone. A similar drowning out occurs in wire- 
less transmission, and when several stations are send- 
ing simultaneously on approximately the same wave 
lengths it becomes practically impossible to select a 
desired message unless it is noticeably stronger or of 
different audible group frequency pitch than the re- 
mainder of the impulses. It frequently happens that 
six or more stations are sending simultaneously with 



20 Experimental Wireless Stations 

approximately the same wave length and with strong 
apparatus, making it nearly impossible to receive an 
intelligible message from a single one of them. Fur- 
ther, when a long distance message is being received, 
and another station sending at approximately the same 
wave length and situated in the neighborhood of the 
receiving station starts in, the result is obvious. To 
be sure, apparatus has been developed which makes 
the selection of desired signals, to the exclusion of 
others, certain within limits, but such cases as the one 
mentioned can usually not be entirely avoided, with 
the best of the present apparatus. This has recently 
been overcome by phase modifying means. When the 
stations are all sending at wave lengths which differ 
considerably from one another and are sharply tuned, 
the desired message can generally be received without 
much difficulty. However, if untuned or only loosely 
tuned signals are sent out from a moderately strong 
or •neighboring station, it becomes ordinarily impos- 
sible to tune them out because they are received by 
forced oscillations. It is like trying to hear a phono- 
graph a block away when a band is playing within a 
few feet of your ears. 

When tuned or sharply tuned waves are spoken of, 
it means waves such as are transmitted from tuned 
transmitting stations so that it is necessary to tune 
within a very few per cent in order to receive them. 
When untuned or forced oscillations are spoken of, it 
means waves which may be received without sharp 
tuning or signals which have several wave lengths 
without any definite characteristics. This is the sort 



Atmospheric Disturbances 21 

which is so generally employed by beginners and even 
by commercial stations in some cases and can be re- 
ceived by all stations within range without any special 
effort. This property is certainly useful in case of 
emergencies at sea, but in ordinary transmission the 
stations with untuned wave transmission should be 
gotten rid of as soon as possible whenever they inter- 
fere with other stations. The matter of tuning will 
be more fully taken up later. 

The only other natural condition of importance 
which affects wireless transmission is the matter of 
atmospheric disturbances. Ordinary strays resemble 
the disturbances caused by untuned waves and are 
practically impossible to entirely exclude, particularly 
when they are present in a large quantity. Certain 
localities have less trouble from stray interferences 
than others, but there are only a few localities in 
which static does not cause more or less trouble. In 
cases of local electrical storms, transmission or recep- 
tion becomes impracticable and even dangerous. Ap- 
paratus recently developed, however, practically miti- 
gates the effects of strays and makes reception pos- 
sible even during thunderstorms. 

The sending and the receiving stations of a wireless 
system are similar and the same aerial capacity may be 
used for both sending and receiving. The receiving 
apparatus of an up-to-date wireless system generally 
includes a detector to detect or rectify the incoming 
oscillations, sensitive recorders, which generally take 
the form of telephone receivers, to receive the intelli- 
gence, and various inductive and capacity apparatus 



22 Experimental Wireless Stations 

to tune the station to receive desired signals to the ex- 
clusion of undesired signals. 

These points and the practical considerations which 
they involve will be discussed in detail in the follow- 
ing chapters. 

The reader should always bear in mind that the 
radiant energy used for wireless work is as real as is 
the radiant energy of the sun. The length of the elec- 
tric waves with which we are concerned can be con- 
trolled at will and while they may be made a fraction 
of an inch or several miles long by merely altering the 
oscillatory circuit as described in Chapter V, practi- 
cal work is at present carried out within 150 to 16,000 
meters. 

One of the principal recent advances has been in the 
direction of stray mitigation. The reader can obtain 
some of the benefits thereof which are not too com- 
plicated for private use by employing a multiturn coil 
or underground receiver with special circuits as de- 
scribed in Chapter III. 

The matter in this chapter is only a mere outline of 
the many conditions involved in wireless transmission, 
and the reader is referred to works by Pierce, Fleming, 
Eccles, Zenneck, Austin, Murray, and others, for fur- 
ther accounts of the history and theories of wireless 
transmission. The mathematical reader will find these 
volumes of particular interest. 



CHAPTER II 
Aerials 

The Antenna; Dimensions; Supports; Height and Length; 
Various Types; 200 Meter Design; Table for Various 
Wave Lengths; Radiation Resistance; Capacity and In- 
ductance; Insulation and Construction; Poles and Guy 
Wires. 

The essential conditions for wireless transmission 
have been briefly outlined and we will now take up 
the matter of aerials. It will be remembered that 
short waves are more easily dissipated than long 
waves. This is particularly true during the summer 
months and when the transmitting station is in the 
vicinity of a large number of trees. Both the sun- 
light, and the foliage on the trees tend to absorb the 
shorter waves to a greater extent than the longer 
waves. Perhaps it is well to more fully define what 
is meant by wave length at this time. 

Now the electromagnetic waves which are gener- 
ated and radiated at the sending station are similar 
to light waves in that they have the same velocity 
(186,000 miles per second) in air of the same temper- 
ature and pressure, have the physical properties of re- 

23 



24 Experimental Wireless Stations 

flection, refraction and polarization, but are different 
in that light waves have a relatively short length while 
the electrical oscillations have a relatively long wave 
length. It may be explained also, that the length of 
a wave means the distance between like points on any 
two consecutive waves. It will be remembered and 
noted that the transmitter of a wireless station sends 
out a series of waves at a very rapid rate, so that by 
the time one has left the aerial and another leaves, the 
first will have traveled a distance roughly equal to the 
wave length. Since these wave impulses occur at a 
very rapid rate (high frequency), a single transmitted 
dot may be made up of several wave impulses. 

The aerial capacity or antenna consists of metallic 
conductors insulated from foreign objects and elevated 
in the air. It is generally made up of a number of sim- 
ilar wires, and its purpose is to radiate electromagnetic 
waves when used as the aerial for a transmitter, and 
to receive or regenerate intercepted waves when used 
with receiving apparatus. The aerial itself may take 
a number of shapes and since each has individual char- 
acteristics, different effects are obtainable from dif- 
ferent combinations of conductors. In the early stages 
of the art solid metal or wire network aerials were 
adopted and the experimenters used chicken netting, 
bronze screen and similar materials for aerials, but it 
was soon found that plain conductors separated uni- 
formly were better suited for this purpose. 

Now the dimensions of the aerial determine the ef- 
ficiency of the wireless station and also limit the ef- 
ficient wave length of the transmitted impulses. In 



Aerials 25 

accordance with good practice and in order to keep 
within the regulations embodied in wireless legisla- 
tion,* the experimenter is expected and required to 
limit his experiments to wave lengths which are not 
over two hundred meters long. Now although low 
wave lengths are more readily absorbed and dissipated 
they are also more suited to low power apparatus than 
the long wave lengths. 

In all ordinary conditions and particularly in cities 
having numbers of other stations, the short wave 
length only should be used. It should be remembered 
that the aerial itself is only one of the factors which 
determine the transmitted wave length and that for re- 
ceiving purposes only the experimenter has a variable 
range of wave lengths at his service by employing 
tuning coils, variometers, or if very high wave lengths 
are desired he may use a loading coil. 

Remarkable ranges have been accomplished with 
200 meter transmission and less. Records of several 
hundred miles were obtained. The small aerial can 
be loaded successfully for long wave length reception. 

The first item to consider, after obtaining permis- 
sion to erect a station, is the exact location for the 
aerial support, and the height for the same. As has 
already been pointed out, the higher the transmitting 
aerial is placed above the surface of the earth, the 

* The act of 1912 is still in effect and stipulates 200 meters 
with Yz K. W. as maximum power. During the war private 
stations were closed and sealed up. A recently introduced 
bill H. R. 13159, Nov. 21, 1918, has been abandoned. The 
Navy Dept. has released amateurs from war-time restrictions. 



26 Experimental Wireless Stations 

better. When only occasional (and receiving) ex- 
periments are to be conducted, a tandem of kites, pref- 
erably box kites, will serve very well. The unsteady 
height resulting from the rising and falling motion is, 
however, not suited to delicate tuning, since the ca- 
pacity of the aerial is thereby altered. There is no 
limit to the ingenuity which may be called to act in 
the selection of inexpensive aerial supports. A sim- 
ple insulated wire dropped from the roof or an upper 
story of an apartment house, flat, water tower, or sim- 
ilar structure to a position some distance below (30 
to 130 feet), will serve as a fair aerial. Insulated tele- 
phone cables may be impressed into service for re- 
ceiving purposes alone. Two grounds may be used 
in place of an aerial, if no supports are available. 
Thus the water pipes may be used as an aerial while 
the gas pipes, or a cistern is used as the ground. Or 
the steel frame or tin roof of a building may be used 
for an aerial while another part of another building is 
used for a ground. Even leader pipes and gutters 
have been impressed into service in certain cases. 
Common wire netting suspended from trees or tele- 
phone poles may be utilized. It is always desirable to 
insulate even makeshift aerials and when two grounds 
are used, one should be connected through a condenser 
to the instruments. The author has even made use 
of a small aerial suspended in an attic, a brass bed in 
an upper story of a residence ; and for very short dis- 
tances such common things as dishpans, bed springs, 
and what not! may be utilized if nothing else is ob- 
tainable. During some experiments in Tripoli, Mr. 



Aerials 27 

Marconi is reported to have laid both the aerial and 
a similar set of conductors to act as a ground directly 
on the sand, parallel to the direction in which the sig- 
nals were to be sent. It is said that no aerial sup- 
ports were necessary because the sand was perfectly 
dry and resembled glass in its conducting properties. 
These items are merely suggested as suitable make- 
shifts in case other and more business like arrange- 
ments are not practicable and good results may be ob- 
tained with them by exercising reasonable skill. 

The supports should take the form of natural sup- 
ports whenever possible as this will save considerable 
expense. Thus short extensions to trees, houses and 
building tops, and similar structures make excellent 
supports. Permission may often be obtained from 
the local telephone or light companies to place exten- 
sions on one or more of their poles so that they will 
not interfere with the regular service and some com- 
panies will even give aid if properly approached. The 
author has utilized such poles for his experiments for 
many years. 

For receiving purposes only, no aerial, but the use 
of the multi-turn coil receiver is recommended. This 
is described in Chapter III and is superior to the 
aerial. 

The erection of large poles from the ground up is a 
difficult task and one which had best be referred to 
the company which sells the pole or else to experi- 
enced erectors. They are not needed for receiving 
stations. 

Good straight-grained 2x2 stock is suitable for small 



28 Experimental Wireless Stations 

poles up to 40 feet, and the size mentioned is prefer- 
ably arranged into two or three lengths. Perhaps the 
best support for experimental stations, when natural 
supports are not available, is iron pipe. This form 
of support may also be used in addition to natural 
supports such as house-tops, etc. The height of the 
aerial should always be sufficient to clear objects be- 
tween stations if possible. For experimental purposes 
a height of about 50 feet is a good average, though a 
higher one is preferable when possible. 

After the height has been determined, the other di- 
mension to be considered is the spread of the aerial. 
In many cases a low height can be compensated by a 
corresponding increase in the aerial spread. How- 
ever, since an increase in the horizontal spread of an 
aerial also increases the minimum wave length of the 
transmitted impulses, this dimension must be limited 
so that the minimum wave length will be about 150 
meters if the wave length is to be limited to 200 meters 
or less, the difference being left to the adjustment of 
the transmitting inductance. When possible it is a 
good plan to have a duplex aerial, which is nothing 
more or less than two separate aerials, one for receiving 
and sending in short wave lengths, and the other for re- 
ceiving in the commercial wave lengths, but not for send- 
ing. While this means two separate aerials and should 
be regarded as such, much ingenuity may be used in uti- 
lizing the same supports for the two aerials. Thus one 
may be supported some distance below the other, and sim- 
ilar arrangements may be carried out in a variety of 
ways. The main objection to a duplex aerial is that part 



Aerials 



29 



of the transmitted energy is absorbed by the idle aerial. 
(See Fig. 5.) This can be overcome to an extent by 
placing the two aerials at right angles to each other or 
entirely eliminated by using the multi-turn coil described 
in Chapter III. 

The large receiving aerial of a duplex system may have 
a length of from 100 to 1,000 feet depending on the in- 
dividual conditions, — about 400 feet being a good length. 
The length means the effective length including the sev- 
eral parts. For the vertical, horizontal, or dipped aerial 
(straightaway) the length of one of the wires is the ef- 




Fig. 5. — Examples of Duplex and Combination Antennas. A 1 , 
Receiving Aerial. A 2 , Sending Aerial. 

fective length. (See the figures.) The effective length 
of the T aerial is the length of the vertical part plus one- 
half of the horizontal portion, while that of the reversed 
L aerial is the length of the horizontal part plus the 
length of the vertical portion. In a loop aerial the length 
is the sum of the lengths of the sides of the reversed U 
loop. With the ordinary umbrella aerial, the length is 
roughly equal to the length of one of the uniform aerial 
conductors, as is also the case in a directive aerial having 



30 Experimental Wireless Stations 

several independent and uniform conductors. In order 
to keep within the limits of the standard short wave 
length, an effective length of 120 or 125 feet should not 
be exceeded.* The transmitting aerial should, therefore, 
be made so that the effective length is within this limit. 
It is understood that the length of the lead-in is included 
in the effective length. The effective length is really the 
distance from the transmitting instruments to the aerial 
proper, plus the effective length of the aerial itself. In 
case a long ground lead is necessary to secure a ground 
to the instruments, its length must also be added to the 
effective length. In the latter case, the aerial itself must 
obviously be still further limited. It is suggested that the 
short length can be partially compensated for by making 
the capacity of the aerial correspondingly larger, but this 
must not be carried too far so that the capacity is too 
large for the wave length or for the charging capacity of 
the sending instruments. It is understood that the capac- 
ity of the aerial can be increased by adding more wires 
to it. A large electrostatic capacity in the aerial means 
greater energy and more power in the transmitted waves 
provided the transmitting instruments are able to charge 
it with a sufficient potential. The wires should always 
be arranged symmetrically and evenly spaced in order to 
decrease the effect of mutual induction between the ad- 
jacent wires as much as possible. An increase in the 
conductors of the aerial does not increase the capacity 
to a corresponding extent on account of this mutual in- 
duction. The distance between the respective conduc- 

♦This means that the length of the aerial proper should 
not exceed 75 feet, in order to allow for lead-ins. 



Aerials 



31 



tors of an ordinary aerial should not be less than .02 of 
their common length. Thus in an aerial 100 feet long, 
the wires should be spaced at least 2 feet apart, or even 
more if possible. In addition to increasing the capacity 
of the aerial, an increase in the number of conductors 
decreases the resistance. A minimum of three wires and 
a maximum of 8 or 10 is the range of the number of con- 
ductors suitable for the average experimental station and 
it is not desirable to exceed these limits. Some results 
may, of course, be had with even a single conductor, but 
for efficiency a plurality of conductors is desirable. The 



.Wires 




Fig. 6. — Umbrella Antenna. 



single conductor serves very well for long wave length 
receiving purposes. A wire 1,000 feet or more long 
and 30 feet high may be used with suitable receiving in- 
ductances to obtain signals from the large stations oper- 
ating on wave lengths as high as 15,000 meters. 



32 Experimental Wireless Stations 

The number of conductors used affects the transmis- 
sion more than the reception of signals. It is desirable 
to use two conductors placed 6 feet apart instead of 
four wires only nine or twelve inches apart and the same 
rule may be applied for other dimensions, since much of 
the effect of the extra wires is lost by reason of their 
close proximity. When only two wires are used, they 
should, of course, have a correspondingly increased ca- 
pacity. In any case, the size of the aerial conductors 
should not exceed No. 8, since larger sizes are wasteful 




-Single pofe sw/fcnss 

Uacfin 
o-o-o—o » 

Fig. 7. — A Directive Aerial with Switch Selector. 

and of prohibitive weight. No. 12 is a convenient size 
for experimental aerials. The constructional details will 
be more fully taken up a little later. Stranded wire is 
best, seven stranded phosphor bronze being a favorite 
kind. 

For short wave lengths, the author considers that 
the umbrella aerial or perhaps a modified umbrella will 



Aerials 33 

prove the most satisfactory for transmission because of 
the large capacity which is possible in a small space. A 
suitable form for this type of aerial is indicated in Fig. 6. 
This aerial is called the umbrella presumably by reason 
of its resemblance to the ribs of the umbrella. This ar- 
rangement may easily be converted into a directive aerial 
as shown in Fig. 7, in which form it will doubtless be the 
most useful to experimenters. The several conductors 
are preferably insulated from each other in this case, 
though they may be connected together at the top or 




FIG.IO 
Figs. 8, 9, 10. — Arrangements for Flat-Top Antennas. 

pole end. Each wire is separately connected to a single 
pole switch, preferably of the common porcelain base 
type. With this arrangement, one or more wires may be 
used independently from the remainder, or all may be 
used if considerable capacity for transmitting purposes is 
desired. This form of aerial is well adapted to experi- 
mental purposes and has the additional advantage of be- 



34 Experimental Wireless Stations 

ing mechanically strong and requiring only a single pole 
support. This type of aerial is particularly suited to 
house tops, the roofs of buildings/ and similar places. 

In congested places where the available space for the 
aerial is limited, as on ships, various types of horizontal 
or flat top aerials are used. Experimenters will find these 
types well adapted to their purposes. These aerials are 
also known by names which correspond to their respec- 
tive shapes. The reversed L type is shown in Fig. 8, and 
is highly directive by reason of its shape. The maximum 
radiation is in a direction opposite to that in which its 
free end points and it also receives signals at the best 
from the same general direction. The leads are taken off 
from one end of the aerial, and if the two ends are of 
uneven length, the lead should be taken off from the lower 
end. In the latter case, the aerial is called an inclined 
aerial. When the leads are taken off in the form of a T 
as in Fig. 9, signals are sent and received the best in the 
plane of the aerial, but the directive effect is considerably 
less than with the L type. Instead of taking the leads off 
at right angles it is often necessary or convenient to take 
them at an angle to form an oblique lead. The several 
wires are preferably connected together at one end, al- 
though this is not essential. 

By taking a double lead as illustrated in Fig. 10, either 
as a T or L type, a looped aerial is formed. This inverted 
U type is adapted to close tuning and eliminates humming 
caused by neighboring telephone and power lines. These 
types may of course be considerably varied, but a simple 
form is desirable in order to secure close, sharp tuning. 

Having gained some idea of the several types and gen- 



Aerials Recommended for Various Wave Lengths 35 

eral features of aerials, some of the constructional de- 
tails will now be considered. 

AERIALS RECOMMENDED FOR VARIOUS 
WAVE LENGTHS 

The following dimensions are suitable for four-wire 
aerials of the "L" type with spacing between wires not 
less than 0.02 of the length. The length here means only 
the flat top length, as the lead-in length will vary with 
the location of the set. To find the amount of wire 
needed multiply the length of the aerial and- lead-in by 
four, which gives the number of feet required. As re- 
gards range in miles which such an aerial can in each case 
cover, it should be understood that the size is no limit in 
this respect. The values given are the approximate nat- 
ural wave lengths in meters and can be increased by load- 
ing with inductance or decreased by means of a con- 
denser in series. 



Meters. 


Height 


above 


ground- 


-feet. 


Length in feet 


150 






30 




75 


200 






50 




80 


200 






60 




5o 


200 






30 




90 


250 






40 




100 


300 






60 




100 


400 






80 




130 


500 






60 




180 


600 






80 




230 



The second 200 meter aerial is recommended for ama- 
teur transmitting. 



36 Experimental Wireless Stations 

WAVE LENGTH OF ANY AERIAL 



( v+ t) 4 - 2 ' 



This is best found with a wave meter, but may be 
roughly calculated from — 

L 
W 

4 

where W is the wave length in meters, V the height 
of the flat top in feet, and L the length of the four- 
wire aerial in feet. 

RADIATION RESISTANCE 

This term originated with J. S. Stone and means the equiv- 
alent resistance which would consume the same energy as 
that withdrawn from the sending antenna by radiation. It 
is often used and according to R. Ruedenberg is approxi- 
mately equal to 
1,600 (height from earth to center of capacity of antenna) 2 

(wave length) 2 
ohms, the meter being the unit of length. 
Example; wave length 600 meters 

mean effective height 40 meters. 

1600 x 40 x 40 

Radiation resistance = = 7.1 ohms. 

600 x 600 

INSULATORS 

It is important that the aerial be suspended so that it 
is thoroughly insulated. The insulation should be effect- 
ive during all kinds of weather and faulty insulation 
should be avoided with considerable care if an efficient 
station is desired. 



Insulators 37 

Hard rubber, fiber, and unglazed porcelain are not very- 
desirable as aerial insulators. A material known by the 
trade name of Electrose is made into a number of suit- 
able forms. This type of insulator is also mechanically 
strong, since metal rings are molded directly into the in- 
sulating material. Corrugations are provided to increase 
the distance over which a surface charge must pass and 
also serve to prevent the formation of a conducting film. 

Aerials for transmitting purposes are necessarily bet- 
ter insulated than those used for receiving purposes only, 
but in any case the aerial conductors should not touch 
other partially conductive materials. Common two-wire 
glazed porcelain cleats make convenient insulators for 
small stations. These may be had for a few cents a 
piece. The holes are 1^2 inches apart, so that a single 
cleat is sufficient insulation for a receiving aerial and also 
for a transmitting station in which only 100 watts or a 
one-inch coil is used. 

When more power or larger coils are to be used, sev- 
eral of these cleats may be arranged in tandem. The 
cleats may be joined, and used by passing wire through 
the two holes so that the wire to be insulated is separated 
by the insulator from the wire attached to the support. 
There are various other forms of porcelain and glass 
insulators which may be had at supply houses and since 
they are all used in much the same manner, no further 
comment seems necessary. Strain insulators are useful 
in breaking up the guy wires used in supporting the poles, 
so that the transmitted waves are not unduly absorbed. 
This form of insulator is also useful for the main aerial 
supports. The leads or lead-in wires should be insulated 



38 



Experimental Wireless Stations 



with the same care as the aerial itself. The supports 
which hold the leads should have insulations of the same 
general nature as that provided for the aerial. 

A problem is sometimes presented when it comes to 
bringing the wires into the building. A good way is to 
bore holes for the wires, in a glass window. Heavy por- 
celain tubes placed in holes in the woodwork are also 
suitable for small stations. A fairly good lead-in insu- 

A 




\v/////;/////////// K 


////////////////////// 


V////////Z4F 










£i L.I. 










v/ c<<<<<<<<<<<<^<<<<^ 


^^<<<<<<<<^^ 


£<<<<<<<^<ii 





Fig. 11.— A Simple Lead-in. W, Window. H, Hole in Glass. 
3, Insulator to Take Up Strain. L. I., Lead-in. P, Win- 
dowpane. K, Slide Casing. B, Board with Insulators. T 1 , 
T 2 , Porcelain Tubes. 

lator can be made by using a nest of tubes, one over the 
other, starting with a half inch in outside diameter and 
ending in the largest convenient outside diameter. A 
number of special insulators may be had at supply houses. 



Assembling — Conductors 



39 



See Fig. n for several details of construction for the 
lead-ins. The wires should be anchored by an insulator 
just before entering the building in order to take up the 
strain. 

The general manner of suspending an aerial is illus- 
trated in Fig. 12. The spreaders can be of wood or bam- 
boo. Curtain poles are suitable for this purpose. 
Twisted wires, screw eyes, mast withes and similar or im- 
provised hardware are useful in fastening - the insulators 
and supports. 

ASSEMBLING— CONDUCTORS 

In assembling the aerial conductors and the spreaders, 
it is advisable to arrange everything on the ground first. 
The wires may be of copper, tinned copper, aluminum, 




Insulator 



Wire^ 



tfSpreader 



Fig. 12. — Antenna Spreader. 



40 Experimental Wireless Stations 

or phosphor bronze. Iron wire is not recommended, al- 
though it may be used. The phosphor bronze is the most 
desirable because it is strong, springy, and may be had in 
a standard strand of seven No. 22 B&S conductors. It 
is generally sold by the foot. Stranded conductors have 
a slight advantage over solid conductors. 

Although copper has less than one-half the tensile 
strength of phosphor bronze, it is very easily obtained 
and quite suited to aerials. It has a good conductivity, 
is pliable, can be easily soldered, and may be had in 
strands if desired. Ordinary No. 12 telephone copper 
wire is suitable for experimental aerials. The wire used 
should never exceed No. 16 or its equivalent in fineness 
or No. 8 in coarseness. 

Aluminum is not so good a conductor nor is it as 
strong as copper wire, but it is pliable and very cheap 
when compared foot by foot. The main difficulties with 
aluminum aerials are that the wires are easily broken by 
twisting and that a non-conductive coating soon forms 
which practically insulates the joints unless they have 
been well soldered. 

In using aluminum wires, kinks, bends, and excessive 
strains should be avoided. This also applies to other 
wires. Aluminum is difficult to solder but special solders 
are obtainable which make the operation reasonably sure 
provided the joint is well cleaned to begin with. All 
joints in the aerial should be soldered and it is also ad- 
visable to cover them with a good quality of electrician's 
tape and rubber solution. Loose contacts in an aerial 
cut down the efficiency materially and also make the aerial 
weak mechanically. The high frequency currents must 



Joints 



41 



have as clear and as good a conducting path as possible 
if the waves are to be radiated without considerable loss. 



JOINTS 

Fig. 13 shows a fairly good way to make a joint with- 
out solder. The wires should be cleaned and the joint 
made tight, after which wrap several layers of tinfoil 
about the joint and tape well. When the aerial is con- 
structed with every concern for efficiency, the wires will 
be thoroughly insulated even at the points where they 
make contact with the metal connections of insulators. 



Splice, 



=3nn 




< C^ ' 



^Tinfoil 



Taps 



Fig. 13.— A Splice with Tin Foil Joint. 

This may be done by tape, and the chief object is to 
prevent thermo-electric and galvanic action between the 
dissimilar metals. Fig. 14 illustrates a suitable joint for 
lead wires which prevents the wire from breaking by the 
swaying motion given it by the wind. When electrician's 
tape and liquid insulation are used, a very good water and 
rust tight joint is insured. The wire conductors should 
be kept free from nicks, kinks, and sharp bends, since 
they are easily parted at such points. 



42 Experimental Wireless Stations 

WIRES— SIZE 

Large. spans require larger sizes of wires than short 
spans, since they are subject to greater strains. Numbers 
8 to io are suitable for spans in excess of 200 feet, while 
numbers 11 to 15 are suitable for the shorter spans. In 

rrrrrrrrmTTTrrmrn 




,- Lead in 



Fig. 14. — Lead-in. 



planning the conductors larger sizes should be used when 
aluminum wire is used than for copper, larger for copper 
than for phosphor bronze, and larger sizes should also 
be used according to the increase in the span. 

AERIAL SUPPORTS 

It is always advisable to support the aerial by means 
of pulleys and ropes, so that it may be lowered for re- 
pairs when necessary. Good galvanized pulleys may be 
had at a low price at hardware and supply houses and 
ropes and flexible wires may also be had at these places. 
Flexible wire is preferable to rope, since the latter re- 
quires frequent renewals. The rope or wire should al- 
ways be sufficient in size to take up all the strains as well 



Lead-In Wires 43 

as a large overload. The working strain of manila rope 
may be found by dividing the square of the circumfer- 
ence in inches by 8 for the strain in tons. Thus, to find 
the size of rope required, estimate the weight, allowing 
for excess strains, and multiply the resulting weight in 
tons or fractions thereof by 8. Extract the square root 
to get the circumference in inches. The safe strain for 
wire rope is found by multiplying the square of the cir- 
cumference in inches by .3 for iron and .8 for steel wire. 
For small aerials a good grade of clothes line or clothes 
wire is suitable. Put up an aerial only if you want to 
transmit and then make your supports strong so a heavy 
wind will not blow them down. 

LEAD-IN WIRES 

The lead-in wires should have a capacity equal to that 
of the aerial. Thus, if the aerial is composed of six No. 
12 wires, the lead-ins should have a capacity equal to 
that of six No. 12 wires, and this is preferably obtained 
by twisting six No. 12 wires together. When the lead-ins 
have a smaller capacity than the aerial itself, they offer 
impedence to the high frequency oscillations and the ra- 
diation is accordingly reduced. The lead-ins should al- 
ways be as short and direct as possible and should be 
connected to the lower end of the aerial. When long 
variously twisted lead-ins are used, sharp tuning is prac- 
tically impossible. The lead-in wires are essentially not 
intended to radiate the energy but to conduct it up to the 
aerial, from which point it is most efficiently radiated. 
When this is not possible, the aerial itself should be ex- 



44 Experimental Wireless Stations 

tended directly to the vicinity of the transmitting in- 
struments. The lead-in wires should have nearly a 
straightaway course, i.e., without angles, bends, joints, 
or the like. If the term may be used,— high frequency 
currents abhor all joints, kinks, bends, and other defects 
in the conductor. 

POLES 

While a number of suitable aerial supports have al- 
ready been suggested, a few notes on poles may be well 
taken. Many experimenters will find bamboo an excel- 
lent material for short poles as well as for aerial spread- 
ers. Portable poles may be made from this material. 
Jointed wooden poles are not desirable for poles exceed- 
ing 40 feet in length, a wooden truss work being more 
suitable for larger poles. Experimenters have made poles 
from 100 to 150 ft. high on the truss plan without great 
difficulties. In this form of construction, the pole is 
built up in the form of a long, narrow pyramid with a 
base so that the builders can construct it piece by piece. 
See Figure 15. 

Iron pipe makes a good material for aerial poles. The 
pipe can be had at any plumbers' or hardware supply 
house in nearly every locality. The stock should be what 
is known as "heavy." The pole may be made in sections, 
the lower section being the largest and the upper section 
the smallest of the progression. The sections are joined 
by reducing couplings, and the dealer should be consulted 
for suitable sizes and dimensions. It will be convenient 
to have the dealer cut and thread and fit the pipe unless 



Poles 



45 



the reader has experience and tools for this purpose. The 
pole and the joints should be covered with a water-proof 
paint, such as a solution of asphalt. A hole to support 
a pulley should be drilled near the top, through which 
the rope to support the aerial is passed. It is desirable 



AeriaL 




Fig. 15. — Lattice Tower for Antenna. 

to insulate the pole at its base when such procedure is 
possible. Sockets for this purpose may be made from 
insulating material or purchased from supply houses. 
The dimensions for a 40-foot iron pipe pole follow. 



46 Experimental Wireless Stations 

Sections — three. 

1st. 15 foot length of 2-inch pipe. 

2nd. 15 foot length of i*4-inch pipe. 

3rd. 10 foot length of ^4-inch pipe. 

Reducers of malleable iron. 

1st, between sections 1 and 2 — 2 by 1% i ncn reducer. 

2nd, between sections 2 and 3 — ij4 by 24 i ncn reducer. 

A top ornament or closure may also be provided. 

Guy wires, — four wires at approximately a 30-degree 
angle from the top portion of each section. Size of wires, 
— No. 12 or 14 galvanized iron. The second and third 
sets are preferably broken by means of insulators. 

GUY WIRES 

The experimenter should take considerable care to 
make his aerial strong so that it will not need repairs after 
every little wind blow. The iron pole will not support 
itself without the aid of the guy wires. In the case of 
an umbrella aerial the conductors take the place of the 
top set of guy wires. Small aerials are easily erected 
and the guy wires may be tightened by hand. Turn- 
buckles should be provided for larger poles, however, in 
order to take up the slack. The insulators in the guy 
wires should be placed every ten or fifteen feet and may 
be of the type already described. Strain insulators are 
preferable for this purpose. 

While the matter of aerials has now been considered 
in some detail, the minor details are left to the individual 
resources of the reader, since the conditions vary widely 



Guy Wires 47 

in each case. The matter in this and other parts of the 
book is intended largely as suggestive rather than dicta- 
tive, and various details may be modified, provided that 
the essential principles and dimensions are not violated. 
It is suggested that the umbrella, variable directive aerial, 
T aerial, and directive aerial will be most suited in the 
order mentioned, and that the duplex idea should be 
adopted if it is desirable to receive from the commercial 
stations without interfering with them. 



CHAPTER III 
Coil and Sub-Surface Systems 

i. Multi-turn Coil Receiver; Portable Receiving Long Dis- 
tance Set; Principle of Coil Action; Directional Effects 
of Coils; Types and Construction; Radio Compass. 

2. Sub-surface Radio; Antenna Buried Underground; Rog- 
er's System; U. S. Navy Experiments. 

THE MULTI-TURN COIL RECEIVER 

The "coil" or loop, as it has sometimes been misnamed, 
is valuable as a substitute for the usual antenna circuit in 
radio receiving systems and may to an extent serve also 
for transmitting purposes. 

It has the advantage of being highly directive, small in 
bulk, cheap, portable. It is less affected by strays than 
the antenna but retains the ability when used with oscil- 
lating vacuum tube circuits and amplifiers of reaching 
any range required. 

A coil, for example, consisting of 200 turns of insu- 
lated wire on a frame but four feet in diameter, Fig. 1, 
serves very nicely, even inside of an office building, to 
receive good signals from the European and other dis- 

48 



The Multi-Turn Coil Receiver 49 

tant stations. A signal audibility of 10,000 may be ob- 
tained from the amplifier with this arrangement from a 
sending source three thousand miles distant. 

The shape of the coil does not appear to be material 
for squares, circles, elipses, oblongs and other shape forms 
wound either in pancake or single layer form all suffice. 
A single turn pancake which might be expected to be more 
directional is about equalled by a single layer coil four 
inches wide in this respect. 

The size of the coil is similarly not a critical factor 
and while a smaller coil requires the use of more ampli- 
fication, one four feet in diameter functions to the same 
signals that another fourteen feet square will. 

An explanation sometimes given for the directional ef- 
fect of the coil or loop is that the front portion and the 
rear portion receive the signals out of phase when in 
alignment with the transmitting direction, but in phase 
such as to oppose and give zero when perpendicular to 
this direction as then both sides get the energy at the 
same time but deliver the result in opposition. 

It seems that the electromagnetic component of the 
advancing electromagnetic waves has the principal if not 
sole effect upon the coil and this accounts for its direc- 
tional qualities for the maximum currents will be induced 
therein only when the turns thereof are cut at right 
angles. This directional quality is so good that by mov- 
ing a coil receiving, from one point to another in an auto- 
mobile to afford a baseline gives the direction and to 
some accuracy the distance of the sending station, the 
latter depending upon the baseline used. 

For transmitting purposes the coil seems limited to 



50 Experimental Wireless Stations 

relatively short distances and apparently a coil of rela- 
tively few turns is best therefor. 

As the coil requires no ground terminal and in fact 
does not function well when connected with one terminal 
open for use as an antenna, it lends itself to shielding ex- 
periments because a cage or coil may be wound around it 
at right angles to the turns of the coil and grounded 
through a high resistance without shutting out the sig- 
nals therefrom. Such a shield was found to not entirely 
eliminate strays from the coil receiver, but a metal lined 
box for the receiving apparatus was not employed in the 
test as desired. 

That the coil receives fewer strays has been proven by 
recording the number and intensity of strays received by 
an antenna at the same time under similar conditions. 
The fact that the strays received by the coil are less in- 
tense is no criterion because the signals received are also 
at lower audibility. 

If two coils are placed at right angles to each other 
and properly oriented, only one will receive the particular 
signals while both will be affected by strays. Unfortu- 
nately, though made alike, two such coils are not simi- 
larly affected by all strays except under unusual and oc- 
casional circumstances, some strays affecting both at in- 
tervals while more often one is affected while the other is 
not or more so. 

The coil is most effective in the V plane and the re- 
ceived signals die down as it is tipped more and more 
toward the H plane, but all strays are not eliminated 
therefrom while resting in the H plane. 

The size of the wire employed in the coil is not a 



Construction 51 

critical factor as long as the resistance thereof is kept 
within reasonable limits. A coil consisting of three hun- 
dred turns of No. 31 DSC wire closely wound functioned 
to the same signals but with much less intensity than one 
consisting of No. 16 wire, but as the dimensions of the 
latter were larger the size of the conductor does not 
wholly account for the difference. Smaller wire and 
lesser dimensions can, up to a working limit, be com- 
pensated for by increased amplification. 

CONSTRUCTION 

As shown in Fig. 16, wind 300 turns D.S.C. wire on 
a frame 6 feet square with slight spacing. The winding 
can be in one or more layers and either in pancake or 
layer form. The lead-in need not be over six feet long 
as a coil elevated to the roof of a building only receives 
the same signals that one inside of the same building 
will. Condenser (1) in series with coil (2) is adjusted 
until the proper wave length is attained. (2) may be a 
coil 8 inches in diameter and consisting of 300 turns of 
No. 26 S.C.C. wire. (3) may consist of a two-layer coil 
8 inches in diameter and containing 500 turns adjustable 
in steps of 100 each. The terminal (7) is best connected 
to include about one-fifth of the turns of coil (3) which 
are in use. Condensers (1) and (4) are air variable 
plate types with maximum capacity up to .05 m.f. each. 
Consult Chapter VI to compute values for any desired 
wave length range. (5) is a vacuum tube with either an 
ordinary or an oxide coated filament (8). (9) is a one- 
half m.f. condenser which connects to a vacuum tube 
amplifier (6), preferably of the two-stage type later de- 



52 



Experimental Wireless Stations 



scribed. The wave length of the circuit depends upon 
the inductance (3) and capacity (4) in use as the multi- 
turn coil circuit (1), (2), (10) can easily be brought to 
resonance therewith. When (2) is tightly coupled 
(close) to (3) a distinct "click" will be heard in the 
telephones (11) when (10), (1), (2) is in resonance 
with (3), (4) at the instant that the correct adjustment 
occurs, the tube (5) being, of course, lighted during this 
adjustment. Consult information given later on vacuum 
tube circuits. This is the ideal receiver for the amateur, 
the investigator, and the man who only wants to hear 
time signals and long-distance communications. It may 
also be used for short wave-length work by proper choice 
of inductance and capacity values. 



Mul+i-+urn Coif 

6 Ft. Square 300 Turns 

No.?OD.S.C.Wire 




> Phones 1 



Wavelength ■ 6000 to IS000 Meters 
Fig. 16. — Multi-Turn Coil Directive Receiver. 



There are many possible modifications. For instance, 
the coil (3) itself may be constructed like (10) is so that 



Eadio Compass 53 

the bulb (15) is directly connected to the multi-turn coil. 
This works nicely. Construct the multi-turn coil so that 
you can turn it about and point it towards the station 
you want to hear. When the signals are heard loudest 
you have the correct line of direction. 

By using an open circuit loop inter-wound with the 
coil, the Navy has been able to reduce stray interfer- 
ence. (See paper by Dr. L. W. Austin, read at April, 
1920, I. R. E. meeting.) 

RADIO COMPASS 

A radio compass can be had by mounting the coil s$ 
it can be turned. This may be done by suspending it 
from the ceiling of a room and marking the 360 N, S, E, 
W, on the floor. Amateurs can thereby do wireless de- 
tective work and find out where the new messages are 
coming from as well as locate unknown stations. Law 
violators are accordingly subject to certain detection. 

SUB-SURFACE RADIO 

For receiving purposes only the antenna (Fig. 17) 
may be underground or under water. Signals have been 
heard over a range of thousands of miles in this manner. 
Reception is safe even during a lightning storm with this 
type of antenna. For experimental purposes a single 
wire five hundred feet long and rubber covered with the 
free end insulated also may be inserted fifteen inches 
underground in a ditch dug for the purpose and later 
covered over. The wire should lie on a line with the 
sending station to be heard. Greater depths are less de- 
sirable owing to absorption — though signals have been 



54 Experimental Wireless Stations 

heard in a mine shaft more than 1,000 feet below the 
earth's surface. During the war a large portion of all 
trans-oceanic reception was done on sub-surface an- 
tennas. The ground terminal is used as is customary for 
an elevated aerial. Strays are not entirely eliminated by 
this arrangement but are mitigated considerably. A 
sensitive vacuum tube receiver with amplifier is required 
at the receiver. 

ROGERS' UNDERGROUND ANTENNA 

The U. S. Navy has developed sub-surface linear an- 
tennas demonstrated by J. H. Rogers, a former amateur 
reader of "Experimental Wireless Stations." Rubber 
covered or bare wire are run about one foot under the 

Vacuum tube .-Directional 

receiving apparatus, Eartfy— S . ..*• Antenna 

xeceiviha Antenna f" ^^%B\p^ fc _^**^>- l 
'^Underground \ An ^^ f ^j^J^ 
-3000 Miles ' Re #«£^fe*>5^*i^ 




TransmittingApfp'C^/ 

Fig. 17. — Underground Receiving Antenna. Messages Are Re- 
ceived from the Usual Transmitter with Elevated Antenna 
by Using an Insulated Wire Under Water or Underground 
at the Receiver as an Antenna Connected to the Usual 
Vacuum Tube Apparatus. 

earth's surface in a trench or in short lengths of iron pipe 
interrupted by rubber hose connections, or in tiles. Such 
wires can be used in parallel, one serving as an antenna 
connection and the other as a ground connection to the 
usual receiving apparatus. Marked freedom from most 
strays is noticed but some are still received and have to 
be specially balanced out. Signals are received at low 



Rogers ' Underground Antenna 55 

audibilities so that an audi on amplifying bulb receiver is 
a requisite for success. 

The wire must be stretched in line with the transmitting 
station, as signals coming at right angles to the wire are 
substantially excluded, while those parallel to it are heard 
best. Signals can be heard safely even when a lightning 
storm rages in the immediate neighborhood of the re- 
ceiver. For a given wave length a most efficient length 
of wire is found. For 600 meters this is about 240 feet 
for insulated No. 12 standard rubber-covered wire. 
Usually the grounded antenna is a periodic, that is, re- 
sponds about equally well to many wave lengths, so that 
in fact several differently tuned receiving sets can be 
connected to the same sub-surface linear wires. The 
wires can be worked even in salt or fresh water and to 
considerable depths below the surface. 

In transmission tests the Navy has been able to com- 
municate 36 miles or more with 0.8 ampere in the under- 
ground wires, using the sub-surface antennas. Experi- 
menters can easily verify the results by simply placing a 
single wire, bare or insulated, and three hundred feet or 
more long, one or more feet underground or under water 
in line with the transmitting station desired, and con- 
necting a regenerative audion receiver of the usual type 
to this as an antenna, using the usual ground, or else a 
second similar wire as a ground. Mr. Rogers considers 1 
that currents through the earth affect this type of re- 
ceiver while others, including Commander Taylor who 
did much scientific work on this system, do not consider 
that there is any separate current through the earth ex- 
cept such as results from the horizontal component of 



56 Experimental Wireless Stations 

the advancing electric waves of the type previously fa- 
miliar. It is a remarkable fact that even submerged sub- 
marines carrying a single-turn loop may communicate 
over practicable ranges as well as receive long-distance 
messages. 



CHAPTER IV 
Grounds and Lighting Protection 

Ground Connections; Various Types; Construction; Light- 
ning Protectors; A Safe Radio Station; Underwriter's 
Rules. 

Equally or more important than a good aerial is the 
item of a good ground. The quality of the ground con- 
nection materially affects the efficiency of a station and its 
operating range. Variations in the ground connection 
may cause a difference of failure or success. Except as 
noted in Chapter III, a good ground connection is essen- 
tial to an efficient wireless station. The various means 
for obtaining grounds may be itemized and considered as 
follows : 

GROUNDS IN WATER 

This form consists of a mass of metal suspended in 
the ocean, a lake, a river, a well, or a cistern and forms 
a good connection. In fact, the grounding of ship stations 
through the hull affords a connection almost as good as 
metal. When connection is made to a pump or cistern 

57 



58 Experimental Wireless Stations 

pipe, the iron should be thoroughly cleaned and the con- 
ductor soldered to it. 

IMBEDDED GROUNDS 

A good connection can generally be had by burying a 
large surface of sheet copper or zinc in damp earth, at 
least 12 feet below the surface and preferably more. A 
ground conductor should be soldered to the sheets which 
should be well connected to each other. The sheets may 
be in the form of old copper boilers which may be had 
from the scrap heap, and it is desirable to have a total 
surface equal to a single flat sheet, 10 feet x 10 feet. It 
is good practice to imbed the sheets in between layers of 
coke in order to insure a uniformly good contact during 
the different times of the year. 

IMBEDDED GROUNDS— SPECIAL FORMS 

There are several ready-made grounds to be had in 
the market, but since these are rarely intended for other 
than use for telephone lines and for lightning grounds, 
several of them connected together must be used for an 
effective wireless ground. They consist essentially of 
sheet copper formed so as to present a large surface to 
the ground and in some forms, a coke filling is used. 
Chemical grounds consist of the ordinary imbedded 
ground with layers of coke and calcium chloride, or cal- 
cium chloride alone around the metal. The calcium chlo- 
ride is very cheap and insures a state of moisture about 
the plates at all times. About 50 pounds of coke and 25 



Connection to Gas and Water Pipes 59 

pounds of calcium chloride will suffice in conjunction with 
I oo square feet of imbedded sheet metal to form a very- 
good ground. 

CONNECTION TO GAS AND WATER PIPES 

In the cities, the gas and the water supply pipes are 
commonly used, preferably the latter. Special ground 
clamps may be had from supply houses for a very small 
sum which are adapted for making good connection with 
the pipes. When the pipes are used for a ground it is 
advisable to short circuit the meter by means of a heavy 
piece of wire. The wire from the instruments to the 
ground should be run as straight and direct as possible 
and all joints should be soldered. When several pipes, 
as water, drain, and gas, are in close proximity to each 
other, it is advisable to connect all of them. 

For small stations and also as a separate lightning 
ground, an iron pipe or several iron pipes two or three 
inches in diameter and ten feet long may be buried into 
the ground just outside of the building in a convenient 
position. The lower end is preferably pointed by ham- 
mering the pipes into a V shape. (A blacksmith can do 
this for you.) The ground wire should be thoroughly 
soldered with care to this pipe and the joint covered with 
pitch or asphaltum. If possible this ground should be 
located over a drain pipe or otherwise provided with a 
supply of water. 

INDIRECT GROUNDS 

There are two general types of indirect grounds and 
neither is as desirable as a good direct ground. In one 



60 Experimental Wireless Stations 

form, a second aerial is constructed and suspended in a 
position close to but insulated from the ground. It thus 
forms a capacity or condenser with the ground. This 
type is adapted to close tuning and is convenient when a 
direct ground is impracticable for one reason or another, 
but is considerably less efficient. The other form of 
indirect ground is similar, except that a large mesh work 
of bare wires or a netting is spread over the surface in 
the immediate vicinity of the station without insulation, 
so that it makes both direct and indirect contact with the 
earth.* A very large area must be covered before this 
method is efficient, but it is sometimes used for portable 
outfits, in which case the network is spread out in grass 
or a similar moist surface in preference to other places. 
For experimental receiving purposes a fair ground may 
be had by driving a spike into a tree and making contact 
therewith. The steel frame of buildings may be used as 
a ground if nothing better is obtainable. In any case the 
ground wire should be run direct from the instruments 
and as short as is possible. 

THE GROUND WIRE 

It is not necessary to insulate the ground wire, al- 
though it is advisable to do so. When it is over 200 feet 
in length it should be well insulated to prevent loss from 
induced currents. The use of a ground wire no less than 
No. 4, B. & S. in diameter is advised and even larger 
sizes are desirable. Of course smaller sizes will serve 
for experimental purposes, but the larger size means a 

* Some of the large stations use this form successfully. 



.Protection from Lightning 



61 



better airect ground. Grounding should not be done by 
connecting to gas or electric fixtures, since these are 
often insulated from the ground and in any case afford 
poor connections. 

PROTECTION FROM LIGHTNING 



Wireless aerials do not attract lightning, as the term 
is generally understood, but they do accumulate undesir- 
able static charges during the stormy part of the year. 
When well grounded OUTSIDE of the building, the 
aerial forms an EFFICIENT LIGHTNING ROD and 
actually protects the station and surrounding buildings. 

\p~-Antenna 




To Instruments • 



4t 

Fig. 18. — Ground Switch. 

These facts have been ascertained by the author by nu- 
merous experiments and although his station has been 
struck several times, no damage has ever resulted. Ex- 
periments were carried out with a condenser and gap 
in the aerial during the electrical storms and large charges 
were accumulated and experimented with at such times. 



62 Experimental Wireless Stations 

Inasmuch as the experiment is attended with some dan- 
ger, its repetition is not recommended. In the experi- 
ences of others with which the author is acquainted, sev- 
eral cases have presented warnings. In one case, the 
operator had his ears pierced while receiving (or trying 
to), from which it may be inferred that it is NOT AD- 
VISABLE to operate during severe local storms.* In 
another case, the operator had his aerial, which was a high 
one, well grounded and no harm resulted to it or the 
immediate neighborhood, while a grocery a block away 
was completely demolished. It is always desirable to 
ground your aerial during storms and at all times when 
it is not in use. This is conveniently accomplished by 
means of a double throw switch on the outside of the 
building so that the aerial is grounded to an outside 
ground when not in use. The ground connection should 
be No. 4 B.&S. wire or even larger and very direct. (See 
Fig. 1 8.) The switch should have a carrying capacity of 
25 or 30 amperes. Fifty or 100 ampere switches are the 
standard size. 

AN EFFICIENT LIGHTNING PROTECTION 

This arrangement takes advantage of the fact that 
the high frequency surges abhor impedence from a choke 
coil. The choke coils are, in fact, more advantageous 
than insulators would be. See Fig. 19 for the Connec- 
tions. The main switch, (4), should be able to carry 
30 amperes and when the station is in use the choke coils 

*i.e., unless the multi-turn coil receiver is substituted for 
the regular antenna circuit. 



An Efficient Lightning Protection 



63 



are short circuited by the auxiliary switches so that they 
will not impede the transmitted impulses. This arrange- 
ment prevents the charge from damaging the instruments 
or the building. The choke coils are made by winding 
30 turns of No. 4 B.&S. wire on a large porcelain tube, 
two or three inches in diameter. 

Lightning grounds should always be carried out to 
the outside of the building or station and if the regular 
ground does not meet this requirement, a separate ground 
must be used. Ordinary short gap lightning arresters 
are useless in wireless stations, because the transmitted 



w* 



tow 



** n rj; 



■--SJ> Switch® 



Choke Coils-. 



■DP.Swi+ch 



(3) 



1 1nstruments 



S.RSwitchQj 



Fig. 19.— Lightning Protection Circuit. When Using Instru- 
ments Open (4), Close (1), (2) and (3). When Not Using 
Instruments, Open (3), (1), and (2). Close (4). 

impulses jump the short gap the same as lightning does. 

The lightning protection for a station does not cost 
a great deal and is well worth while. It is one of the 
first items which should receive attention, particularly in 
mountainous regions. 

When the station is not to be used for a long time, 



64 Experimental Wireless Stations 

as during a vacation trip, it is desirable to lower the aerial 
conductors so that the liability to become blown down 
by winds or be struck by lightning is entirely removed. 

It is not necessary to take the aerial down during 
stormy weather, however, or even desirable, provided 
that it is well grounded. 

Attention is directed to the various underwriters' and 
local municipal rules affecting installation of the circuits 
of a radio station. Those who wish a safe workmanlike 
job should follow such regulations. 



CHAPTER V 
The Transmitter and Resonance 

Transmitting Circuit; Principle of Oscillations; Action of 
Energy; Resonance; Period of Vibration; Adjustments; 
Harmonic Effects; Resistance; Beats; Typical Curves for 
Various Transmitters; Damping; Relation of Antenna 
Current and Voltage; Experiment Illustrating Coupling. 

In the present chapter the general features of the trans- 
mitter together with a consideration of resonance will 
be considered, and it is suggested that this matter be un- 
derstood before referring to the chapters on the several 
details. 

To begin with, we are only to consider tuned transmit- 
ters, i.e., those which are coupled to the antenna circuit. 
There are two general types of coupled transmitters, the 
direct coupled and the indirect or inductively coupled. 
Each has certain characteristics which will be considered 
more fully. The exact circuits employed are, of course, 
somewhat varied, but since the general features are the 
same the circuit shown in Fig. 20 may be regarded as typ- 
ical of the direct coupled type, while that shown in Fig. 
21 may be regarded as typical for the inductively coupled 
type. For the present the circuits will be regarded as 

65 



66 



Experimental Wireless Stations 



excited only by means of ordinary spark caps. Other 
means for excitation which are within the limits of the 
average experimenter, will be considered in detail later. 
The first point to be thoroughly understood is that the 
transmitting circuits are oscillatory in nature and that the 
transmitted impulses are radiated as waves having char- 
acteristic properties. In wireless transmitters, the essen- 
tial characteristics of the circuits are that they may be 
caused to vibrate at a very high rate. The phenomenon 
is very much like other vibrations. For instance, in 




Fig. 20. — Typical Transmitting Circuit Diagram. K, Key. B, 
Current Supply. T, Transformer or Spark Coil. S, Spark 
Gap. C, Condenser. I, Inductance Coil. A, Aerial. G, 
Ground. 



sound, if a bell is struck a sharp blow, it vibrates and the 
vibrations in turn cause sound waves to be radiated from 
the surface of the bell. The loudness of the sound will 
vary according to the dimensions of the bell and the force 
with which it is struck. The tone of the resulting sound 
will also vary according to the dimensions of the bell it- 



The Transmitter and Resonance 



67 



self, i.e., its characteristic dimensions and vibratory pe- 
riod. 

In a wireless transmitter, we have the same features. 
The current which causes a high potential to charge a 
condenser, corresponds to the force which strikes a bell. 
The condenser in turn sets up vibrations in the circuits 
so that waves are radiated from the antenna, in much the 
same manner as the vibrations of the bell cause sound 
waves to be radiated. In fact the difference in the waves 
radiated by the bell and a wireless transmitter lies in 
the characteristic properties (wave length, persistency, 
etc.), and in the medium through which the respective 
radiations are carried. (Air for sound and ether 
(space) for wireless waves.) 

Now then, the circuits of the transmitter can be vi- 
brated tKe same as a bell is vibrated and the character 



rM! 



J 



-T 

V S 



aW 



ITJTinn Loading 
1 Coil 



MO 



i 



Fig. 21. — Inductively Coupled Transmitter. 



of the radiations will vary according to the electrical di- 
mensions of the circuits and the force with which they 
are set into vibration. This is the keynote to an under- 



68 Experimental Wireless Stations 

standing of the why of wireless transmission. We can 
vary the characteristics of the transmitted radiations by 
changing the electrical dimensions or vibratory period of 
the transmitting circuits. This is accomplished by adding 
or subtracting capacity or inductance or both, in much the 
same manner as a violinist varies the effective length of 
a given string to produce different tones. It is under- 
stood that even the slightest change in the capacity or in- 
ductance of a circuit changes its electrical dimensions 
and also changes the period or rate of vibration. The 
actual vibration in the circuits is caused by the surgings 
of the discharge from the condenser, or as is more often 
termed, the oscillatory discharge of the condenser. 

By the referring to Fig. 20, in which A represents the 
aerial, G, the ground, I, the inductance which may be 
varied and which also couples the condenser and the an- 
tenna circuits, C, the condenser, S, the spark gap, T, a 
transformer or spark coil, B, a source of current and 
K, a circuit closing key, it will be obvious that when the 
key K is closed the transformer or coil T, which is wound 
to produce a high potential at the secondary terminals, 
will cause a spark at the gap S. In practice the gap and 
the condenser are adjusted so that the condenser is first 
charged and then discharged through the gap S. Now 
it has been definitely proven that although the coil T only 
produces a secondary current at its terminals with a fre- 
quency of say 120 cycles per second, this same current 
when used to charge the condenser C and subsequently 
discharged through the gap S, causes an oscillatory cur- 
rent to discharge in the gap S which may have a fre- 
quency enormously greater than the original frequency of 



The Transmitter and Resonance 69 

120 cycles per second. This high vibration may, in fact, 
be as much as 250,000 per second or even more. It is this 
high rate of oscillation in the condenser circuit which 
causes radiations to be sent out, as has already been ex- 
plained. The condenser circuit through the gap S, and 
the inductance I (the oscillations do not pass through the 
secondary of T on account of the high resistance offered), 
is the actual part of the wireless transmitter which corre- 
sponds to the hammer of a bell. If differs from a simple 
comparison, however. It is found that the exact nature 
of the resulting vibrations depends on the dimensions of 
the several parts, S, C, and I. It will be obvious that 
the condenser in discharging through the circuit I, S, C, 
at a very high rate causes the turns of I through which 
it passes to vibrate at a corresponding rate. The oscilla- 
tions are thus made useful for transmission purposes by 
forcing them to pass through a part of the inductance I. 
Now it is further found, that if the dimensions of circuit 
C, I, S, are changed, as by adding or subtracting capacity 
or inductance, that the characteristic properties of the 
resulting oscillations are varied, in much the same man- 
ner as the tone from a bell is varied if a lead weight is 
attached to its edge, or a violin string, if its effective di- 
mensions are varied by the fingers of the violinist. • 
In further considering the circuit C, I, S, it should 
be understood that for the maximum effect, the several 
parts C, I, S, must be adjusted or varied so that they mu- 
tually contribute to produce the maximum effect. It is 
obvious that if there is too much capacity, the circuit will 
be unbalanced and consequently the coil T will not be 
able to fully charge it. Or if the gap S is too long the 



70 Experimental Wireless Stations 

condenser will not discharge through it, while if too short, 
the condenser will not be fully charged before it dis- 
charges. Or further, if the number of turns of I in the 
circuit is too many or too little, the circuit will also be 
unbalanced. In any case or combinations of any single 
cases, the result will be similar to that when an excessive 
weight is attached to the rim of a bell, that is, the circuit 
through C, I, and S, cannot vibrate properly. If the dif- 
ference between the adjustment and the ideal adjustment 
is not great, the oscillatory effect will not be stopped, but 
the properties of the oscillations will be correspondingly 
varied. In practice it is generally found that there is a 
certain adjustment for the circuit which produces a max- 
imum result. It is, of course, understood that any change 
in the dimensions of the parts of the circuits causes a 
change in the natural wave length of the circuit and the 
resulting oscillations, the same as changing the diameter 
of a bell produces a different tone. Changing either the 
inductance or capacity in even small amounts causes a 
noticeable change in the wave length and intensity of the 
resulting oscillations. The parts of the circuit have been 
arranged in definite mathematical formulas so that the 
proper dimensions for the several parts to produce a 
given result for a station can be worked out by a sim- 
ple mathematical operation. This feature will be con- 
sidered a little later. 

Now, then, by referring to this same figure (20), it 
will be obvious that when an oscillatory current passes 
through some of the turns of I, that oscillations will also 
be set up in the antenna circuit A, I. G, by mutual induc- 
tion between the portions of the turns of I included re- 



Kadiations 71 

spectively in the antenna and in the condenser circuit. 
The ratio and relation of the respective turns included in 
the antenna and the condenser circuits determine the de- 
gree of coupling between the two circuits. The oscilla- 
tions in the inductance I are of very high frequency, as 
has already been explained, and the two portions of the 
inductance act as a transformer. The inductance I forms, 
in fact, an auto-transformer (step up). Now then, the 
voltage as well as the frequency through the part of I 
included in the condenser circuit is very high so that the 
frequency through the antenna circuit is of substantially 
the same frequency but a much higher potential, on ac- 
count of the ratio between the turns included in the two 
respective circuits. The antenna circuit is thus supplied 
with a very high potential oscillatory charge, correspond- 
ing to. the oscillatory discharge of the condenser C. The 
antenna circuit is consequently very powerfully vibrated 
and as a result radiations are transmitted from this cir- 
cuit in much the same manner as sound waves are trans- 
mitted from the surface of a bell, except the sound waves 
are transmitted through air, while electromagnetic waves 
are transmitted through the ether and are caused by 
the intimate relation of the vibrating antenna circuit with 
the ether, which presumably disturbs the ether at a cor- 
responding rate. It is understood that the term "ether" 
is the name for an all prevailing material which is as- 
sumed to exist and to carry this electrically generated 
vibratory motion in the same general way in which the air 
carries the sound waves.' 

Now the exact nature of the radiations is determined 
by the dimensions of the antenna and condenser circuits, 



72 



Experimental Wireless Stations 



while their power is determined by the primary generating 
source as well. 

INTERCHANGE OF ENERGY IN SPARK 
TRANSMITTER 

Graph I, Fig. 22, shows how the oscillating energy re- 
peats from the primary to the secondary or antenna cir- 
cuit and vice versa. When the energy is a maximum 



"firne-v 




Secondary Oscillation Circ 



Fig. 22. — Graph. I. Energy Oscillations in Transmitting Circuits. 

in one circuit it is a minimum in the other. This is an 
undesirable feature obviated by more modern transmit- 
ting equipment. 



RESONANCE 

Resonance in the transmitter means the attuned, or 
syntonic relations in and between the condenser and an- 
tenna circuits and is also further carried out between the 



Resonance 73 

condenser and the transformer or coil T, when maximum 
results are desired. In Fig. 20, the condenser C, and 
transformer T are in resonance when the capacity of C 
is adjusted so that it is just enough and not too much to 
efficiently and economically receive a charge and dis- 
charge the same. This relation can be determined by a 
simple mathematical operation from a formula, which 
will be fully presented later. Now, then, with the con- 
denser determined, its capacity must necessarily remain 
the same for a given coil T, so that if the circuit through 
C, I, and S, is to be brought into resonance, the respec- 
tive parts must be suited to the given capacity. The gap, 
S, is of itself a minor item, the essential features being 
an ability to handle the full discharge currents without 
undue heating and to be of the proper length so that the 
condenser is properly charged and discharged. The main 
tuning, then, must be done by increasing or decreasing 
the number of turns of the inductance I, through which 
the condenser circuit must discharge. Now a wire or 
ribbon conductor, such as is used for constructing the 
inductance I, has both capacity and inductance, though 
the latter is in great excess so that the capacity is nearly 
negligible. In a like manner, the condenser of itself con- 
sists essentially of capacity. Even the connecting wires 
between the condenser and the inductance have capacity 
and inductance, also resistance, so that in order not to 
materially affect the resulting oscillations they must be 
made very short and of large size so as not to impede 
the high frequency oscillations. 

Every conductor has a definite period of vibration for 
electromagnetic waves, just as every wire in a piano has 



74 



Experimental Wireless Stations 



a definite vibratory period. Now the separate periods 
can be combined or superposed when a number of con- 
ductors or circuits are coupled or connected in much the 
same manner that two or more notes from a piano can 
be caused to produce a pleasing or displeasing tone. The 
condenser circuit, then, is made up of several parts which 
must have very little resistance and practically no stray 
inductance or capacity. Now, increasing the number of 
turns through which the condenser circuit passes also in- 
creases the time of the vibrations, causing a correspond- 
ing increase in the wave length. The wave length of the 
oscillations in the condenser can thus be varied by adding 
or subtracting the desired amount of inductance through 
which they pass, and the less the number of turns of in- 
ductance included in the circuit, the less will be the wave 
length. 

Now then, consider the resonant relations in the an- 
tenna circuit. It is understood that the antenna itself, 



*—m 



J 



aW 



Variable 
Condenser 



f 



Fig. 23. — Transmitter; Direct Connected Through Inductance. 



being made up of a plurality of spaced wires, consists 
essentially of capacity and also quite a little inductance. 
The antenna forms the capacity of the circuit in conjunc- 



Resonance 75 

tion with the ground. The inductance of the circuit, then, 
will be the variable factor since the antenna is generally 
a fixed item. The wave length of the circuit A, I, and G, 
then, will be varied according to the variations in the 
amount of inductance or turns of 1, included in the cir- 
cuit, in the same manner as has already been explained 
for the condenser circuit. 

That is, when the number of turns of I, through which 
the antenna circuit is included, is increased, the wave 
length of the circuit will be increased. It will be obvious 
that since A is a .fixed quantity the natural wave length 
of the antenna circuit cannot be less than that of A and 
G without inductance,* in the circuit shown in Fig. 20, 
and that the variations must then be limited to increase 
the wave length of the antenna system. As in the case of 
the condenser C, when the maximum results are desired, 
the capacity of the antenna A must be made the proper 
amount to begin with. This can be accomplished by using 
the length and number of wires which will produce a 
capacity and inductance within the limits of the minimum 
wave length desired. It is possible to lower the wave 
length by means of circuit like that of Fig. 23, in which 
a condenser is connected in series with the ground cir- 
cuit, but this method is not very desirable. In view of 
the limited wave lengths, to which experimenters are 
legally assigned, this method can be utilized in cases in 
which aerials already in use slightly exceed the maximum 
wave length. The disadvantage of this arrangement is 
that the transmission is less efficient. 

But to return to Fig. 20. In order that the antenna 

* See Fig. 23 for exception. 



76 



Experimental Wireless Stations 



and condenser circuits should be in resonance with each 
other, it is necessary that the adjustments of the induct- 
ance I, be made so that the wave length of the condenser 
circuit is the same as that of the antenna circuit. The 
circuits will then be in a position to produce a maximum 
radiation. This condition is, however, difficult to obtain 
exactly and is further complicated by the phenomena of 
beats, that is, the oscillations in the two circuits super- 
pose and interfere with each other so that two wave 
lengths are produced instead of one. This feature will 
be presently more fully discussed. Now if the circuits 
have been brought into resonance so that they are both 
attuned to, say, 300 meters wave length, and if it is de- 



- 


4 

T 

TT 



000001 



mm. 



i 



Fig. 24. — Loose Coupled Transmitter with Loading Coil. 



sired to increase the transmitting wave length, both cir- 
cuits must be increased accordingly. The wave length of 
the condenser circuit is increased by adding more turns 
of inductance and the maximum wave length for the 
condenser circuit will be reached when this circuit in- 
cludes all of the inductance. Since the wave length de- 
pends on the product of the inductance and capacity of a 
circuit, the maximum wave length of the antenna circuit 



Resonance 77 

will generally be reached before the maximum wave 
length of the condenser circuit is reached, so that after all 
of the turns of the inductance of the coil I, have been 
included in the antenna circuit, the wave length cannot 
be further increased. Increasing the inductance of the 
condenser circuit in this case will throw the circuit out 
of resonance. The wave length is thus limited by the di- 
mensions of the antenna A and the inductance I. Since 
it is impractical to have the inductance I too large and 
since the antenna A is in practice a fixed quantity, the 
arrangement of Fig. 24 must be used if extra long wave 
lengths are desired. This method acts to increase the 
natural wave length of the antenna circuit. The shunt 
antenna condenser (v. c.) may be omitted if desired. 
The extra inductance is known as a loading coil and ex- 
tremely long wave lengths may be obtained in this 
manner. As in the case of Fig. 23, however, the effici- 
ency of transmission is considerably lowered, since 
there is generally a limited range of wave lengths at 
which a given station can economically operate. How- 
ever, for experimental purposes, this arrangement can 
be used to attain very long wave lengths (those ex- 
ceeding 1,500 or 2,000 meters in length), a field as yet 
open only to the experimenter who obtains a special 
license therefor. 

There is one other case of resonance with which the 
experimenter is concerned. When spark coils or adjust- 
able types of transformers are used in connection with 
adjustable condensers in the condenser circuit, there may 
be more than one adjustment of the condenser C, which 
will produce a maximum resonance effect with the in- 



78 Experimental Wireless Stations 

ductance of both the antenna and the condenser circuit 
in a fixed ratio. This is a peculiar harmonic effect * and 
it is remarkable that a maximum effect can be had with 
different adjustments of the capacity through essentially 
the same circuit. Now when the power used in the coil 
or transformer T is decreased (as when transmitting 
over a very short distance), the condenser C, and the 
other adjustments should also be changed if the maxi- 
mum effect is to be carried out. To sum up : 

The resonance relations and wave length of a trans- 
mitter depend on the relations of the circuits and the ad- 
justments of the several parts. Since some of these parts 
are of fixed dimensions, the others must be adjusted to 
correspond with them and co-operate to produce resonant 
circuits. The order of tuning is practically, — 

1. The transformer or coil being fixed, the condenser 
must be varied to resonate with it. If the power is 
changed, a corresponding change must be made in the 
condenser if the maximum effect is to be preserved. 

2. With the condenser a fixed quantity, to produce a 
given wave length in the condenser circuit, the inductance 
must be varied to co-operate with the capacity, and al- 
though the wave length may be greatly increased, the ad- 
dition of excessive inductance cuts down the transmitting 
efficiency. 

3. The aerial being a fixed quantity, the antenna cir- 
cuit can be adjusted for a desired wave length by the ad- 
dition of inductance, but if too much inductance is used, 

* The same effect is noticed at receiving stations. 12,000 
meter signals can sometimes be advantageously received on 
a set adjusted to 6000 meters. 



Resistance 79 

with or without a shunt capacity, the efficiency of trans- 
mission is reduced. A series capacity may be used to 
diminish the natural wave length. 

4. The wave length of the two circuits should be very 
nearly the same, and if one is changed, the other must 
also be altered. In short, the several circuits and parts 
must be maintained in a nice balance in order to obtain 
the maximum results and resonance. This balance must 
be kept within the limits of the power employed in order 
to maintain the efficiency of transmission. This means 
that the small stations are naturally limited to small wave 
lengths, while large stations may be operated at longer 
wave lengths without appreciable loss, and often with 
gain. 

The relations in the circuit of Fig. 21 are very similar 
to those of Fig. 20, and the adjustments are carried out 
in the same manner. In fact, the chief difference in the 
two circuits is in the matter of the coupling, as the effect 
is essentially the same in other respects. 

In this arrangement the antenna and condenser cir- 
cuits include the primary and secondary of a mutually 
inductive system which is not directly connected. The 
relative distances between the two coils is also made ad- 
justable in practice, so that the coupling can be varied. 
The chief advantage of this arrangement is that it per- 
mits of sharper tuning, but it has a disadvantage in that 
this is accomplished at the expense of the intensity of the 
resulting radiations. 

RESISTANCE 

Resistance is an important item in a wireless system. 



80 Experimental Wireless Stations 

The high frequency oscillations travel over the surface of 
a conductor only and do not penetrate into the body of 
the conductor, as in the case of low frequency currents. 
Plenty of conducting surface must therefor be provided 
in both the condenser and the inductance coil as well as 
in all connecting wires or ribbons. Otherwise, a large 
amount of power is wasted in heat. Resistance also aids 
in preventing sharp tuning, so that there is an added rea- 
son for making r II the parts of the transmitter of large 
and generous dimensions. A further desideratum is that 
all of the circuits as well as the several parts, including 
the antenna itself, should be as uniform as possible. That 
is, the several conductors should be as direct as possible, 
all joints electrically strong, the aerial well insulated, the 
ground good, the spark gap well cooled, and the several 
contacts always well made. Observance of these items 
together with reasonable skill in attuning the several cir- 
cuits is sure to produce very satisfactory results. Some 
modern sets use braided copper wire for connections. 

SHARP TUNING— BEATS 

Reference has already been made to the phenomenon of 
beats in a wireless transmitter. Now it has been estab- 
lished, that when the condenser and antenna circuits are 
coupled by either the direct or inductive method, the 
primary or condenser circuit has two periods of oscilla- 
tion instead of one, and that the secondary or antenna cir- 
cuit has the same two periods of oscillation. This holds 
true with perhaps a few exceptions, in every case, includ- 
ing the ideal coupling of the two circuits adjusted to the 
same wave length. As a result, the transmitter emits two 



Sharp Tuning — Beats 81 

distinct waves instead of one, thereby complicating the 
difficulty of selective receiving from a field of stations, 
still further. This is undoubtedly due to the fact that 
the primary and secondary circuits are alternately charged 
and discharged. The primary circuit starts out at a max- 
imum, the secondary gradually building up while the pri- 
mary decreases until the operation comes around to the 
beginning of the cycle, and is again repeated. The phe- 
nomenon of beats is caused in much the same manner as 
in sound waves and the reader is referred to an elemen- 
tary text on Physics for a further understanding of the 
term. The analogy is complete, when the electromag- 
netic waves are regarded as having similar properties to 
those of sound waves. 

The experimenter is directly concerned with this phe- 
nomenon, in that it materially concerns the matter of sharp 
tuning. Now when the transmitter is in resonance, the 
station is said to be tuned and if the resonance is very 
good, it is said to be sharply tuned. This is the desidera- 
tum of real scientific wireless work. On the other hand, 
when the circuits are not in resonance, the station is said 
to be untuned. 

In this condition the station is only a very little better 
than a direct untuned station (see Fig. 25), and when 
in this condition a wide band of wave lengths are sent out 
which are difficult to tune out. Since this is the kind of 
waves which were formerly largely employed by ama- 
teurs, it has brought forth considerable criticism. Even 
commercial operators have wilfully or innocently used 
untuned waves or at least poorly tuned waves in the past. 
On account of the large number of stations in operation 



82 



Experimental Wireless Stations 



at the present time, this form of "pick me up wave" is in 
disrepute because it causes unwarranted interference. At 
any rate it is not scientific or business-like and is soon 
to be stopped. In fact, it is equally or more important 
to have a sharply tuned station than to have one of lim- 
ited wave length alone without sharp tuning. By rea- 
son of the limited wave length, tuning among experi- 
menters themselves will become all the more difficult 
on account of the limited range, and the sooner all 
amateurs install and operate sharply tuned instru- 



IE5 

JZL 



Fig. 25.— Untuned Direct Connected Transmitter. 

ments, the better it will be for all concerned. To make 
this clear, some curves submitted to the radio com- 
munication committee of the House of Representatives 
by Mr. Kolster of the Bureau of Standards are repro- 
duced here. (Figs. 26, 27, 28.) 



Sharp Tuning — Beats 



83 



These curves are plats to show the amount of energy 
received under different conditions. By referring to chart 
A the figures, 600, 700, 800, etc., at the b6ttom indicate 
wave lengths in meters. The numbers at the side of the 
sheet (95 to 140) represent the strength of the signal re- 




800 900 1000 
Wave Length 

Fig. 26.— Chart A. 



1200 



ceived at the receiving station. Thus at 600 meters, the 
strength of the received signal is 105. At 700, it is 
stronger, approximately 127, and so on. The curve thus 
indicates the wave length and the corresponding loudness 



84 



Experimental Wireless Stations 



of the signal. The signals are the loudest between the 
wide range of 700 and 900 meters, and were taken from a 
ship station. The station is sending out a wide band of 
wave lengths (750-950 meters), so that it is sure to inter- 
fere with other stations. At a short distance, within, 
1,100 meters the current makes another rise. That is, the 



us 
140 

135 

c 



£130 

c 

+• 

to 

en 

j» 

5 

u 
V 

+- 120 


« 


c 

.7115 
%r> 



«/> 

S 110 

c 

"0 

D 
O 

-J 

105 
100 

OR 






n 
































































n 














/ 


























/ 


I 












/ 










1 






\ 







700 800 900 1000 

Wave Length 

Fig. 27.— Chart B. 



1 100 



1200 1300 



Sharp Tuning — Beats 



85 



particular station under consideration sends out a sec- 
ond wave length denned at 1,100 meters as well as the 
broad band of 700-950 meters. This station is not send- 
ing out any definite wave length, so that it interferes with 
MO 



135 



130 



O) 

I 125 

'5 
u 

■ 



120 



6 

:f 115 



105 



no 







A 












11 




















































































/ 









700 800 900 1000 

Wave Length 

Fig. 28.— Chart C. 



1100 



1200 1300 



all other stations within a considerable range. Amateurs 
in the past have in some cases sent out wave bands of 
similar dimensions so that the meager efforts of commer- 



86 Experimental "Wireless Stations 

cial operators to tune out interference with crude ap- 
paratus have been of little avail. 

The chart I shows the double wave length from an or- 
dinary spark excited commercial station, one wave being 
approximately 830 meters and the other 980 meters. The 
chart indicates that the station concerned was very badly 
tuned. As a contrast to this chart, the curve of chart 3 
may be noted. This was made from a well tuned modern 
wireless set and the signals are sharply defined within a 
range of 75 meters.* This means that a difference of 75 
meters would entirely cut out this station under good con- 
ditions. 

While details of tuning will be again discussed, it is 
thought that every reader must realize the importance of 
sharp tuning, resonance, and definite wave lengths. 

DAMPING 

The damping of electromagnetic waves may be com- 
pared to sound waves as in the case of the other proper- 
ties. That is, damped electromagnetic waves correspond 
to the sound which is emitted from a bell when a soft ob- 
ject such as the finger touches it, so that the vibrations 
are limited. This is a common experiment and when a 
similar property is understood for electromagnetic waves, 
the term 'should not be difficult to understand. 

Undamped waves, then, are those which are free to 
vibrate while damped waves are those which are more or 
less hampered. f Now, absolutely undamped waves are 

* Refers to a Quenched Spark Set. 

f Perfectly undamped waves are not obtainable in practice 
but can be approximated by using arc or vacuum tube cir- 
cuits. These are discussed later. 



Damping 87 

practically impossible, but the nearer the transmitted 
waves approach this point, the more efficient will be the 
transmission, just as the sound from a bell is greater 
and lasts longer if the bell is free to vibrate without im- 
pedance. When the transmitted waves meet considerable 
impedance, they are said to be damped or strongly 
damped and in this condition are not very efficient for 
wireless transmission. The damping is caused largely by 
the resistance which the circuits offer to the oscillations 
and generally speaking, the conditions for undamped 
waves require a minimum resistance. 

The ordinary spark system with a close coupled cir- 
cuit, similar to that of Fig. 20, emits waves w T hich are 
more or less damped, depending upon the adjustment, 
while the arrangement of Fig. 21 emits waves which are 
less damped, the other conditions being practically the 
same. In the arrangement of Fig. 21 the coupling is 
free, so to speak, so that the vibration of the antenna cir- 
cuit is not greatly impeded, while in the arrangement of 
Fig. 20, the antenna circuit has a close coupling with the 
condenser circuit so that its vibrations are hampered and 
limited to a considerable extent. Undamped waves or 
continuous waves are a desideratum in efficient long dis- 
tance transmission, and it is for this reason that the 
untuned and even the close coupled circuits are being 
superseded by the inductively coupled circuits. This mat- 
ter will be more fully discussed later on. In order to 
keep the damping to the smallest possible point, it is neces- 
sary to keep the resistance of the circuits down to a 
minimum, and when it is remembered that the resistance 
of a conductor to high frequencies is greater than to 



88 Experimental Wireless Stations 

currents of low frequencies, the need for large direct con- 
ductors should be all the more apparent. 

ANTENNA CURRENT AND VOLTAGE 

In chart D the current and voltage curves for the com- 
mon flat top antenna are shown. At the ground (i) the 
current is maximum and voltage minimum, and vice versa 




Fig. 29.— Chart D. 

at the free end (2) the current is nearly zero while the 
voltage is at the highest value. 

EXPERIMENT ILLUSTRATING COUPLING 
BEATS 

In Fig. 30 a simple set to study the effect of coupling 
mechanically is shown. With (1) at rest, start (2) 
swinging and note result. By varying the length of 
string and distance between (1) and (2) all of the cases 
including resonance (when maximum swings are trans- 
mitted from one pendulum to the other which is coupled 



Experiment Illustrating Coupling Beats 89 



to it) may be studied. Set it up on the backs of two 
chairs if you want a good idea of what happens when two 





N 




r 




Support 



String 12 Ft Long 



String 6 F* Long 



■0 




M. 



Support 



*0 



I Lb Weight 



Fig. 30. — Experiment Illustrating Coupling Interaction Between 
Two Circuits. 



electrical circuits corresponding to (i) and (2) zx% in- 
ductively coupled together. 



CHAPTER VI 
Wave Length, Capacity, and Oscillation Circuits 

Damped Wave Transmitter; Calculation of Wave Length, 
Capacity, and Circuits; Range of Transmission; Power, 
Frequency and Voltage; Table of Capacities; Formula 
for 200 Meter Calculations; Spark Gap; Antenna Cir- 
cuit; Percentage of Coupling; Example of a Complete 
Spark Transmitter; Dimensions. 

In planning the transmitter, the main conditions which 
govern the design are the distance over which the trans- 
mission is desired, the number of stations and their loca- 
tion, to which it is desired to communicate, the local and 
intervening conditions, such as the condition of the soil, 
atmosphere, and other natural conditions, and the item 
of expense. 

Perhaps the matter of expense is the main item and 
it is always desirable to keep within defined limits. The 
expense does not follow directly according to the trans- 
mission distance and will, in fact, vary considerably ac- 
cording to the conditions in each case. The actual 
amount depends on the price paid for raw materials, 
labor, transportation, and since all of these items are va- 
riable, the exact amount must be figured for each case. 

90 



Range of Transmission 91 

Thus, if the raw materials may be obtained so that no 
transportation charges have to be paid, or if the apparatus 
can be had second hand, or if the labor is negligible, and 
so on, the cost will be materially reduced. Ordinary ex- 
perimental stations do not entail a great deal of expense. 
While everything should be made as workmanlike and 
businesslike as possible, extraordinary finishes and pol- 
ishes are not essential to success. 

RANGE OF TRANSMISSION 

While this cannot be accurately determined to begin 
with, it may be approximated to a sufficient extent. The 
experimenter generally has a few definite stations with 
which direct communication is desired and in all cases 
which permit the use of a directive aerial, this type should 
be adopted for the purpose specified. When communica- 
tion is desired in all directions, the umbrella or T type 
aerial will be the best to adopt. The distance to which a 
given station can send is governed largely by natural con- 
ditions, such as character of the soil, foliage, mountains, 
minerals, height of aerial, and other similar items, as well 
as the per cent of efficiency which the apparatus is capable 
of, by itself. The variables are so great that while trans- 
mission has been carried out over a distance of ioo miles 
or more by the use of a one-inch spark coil at an expendi- 
ture of perhaps ioo — 200 watts, there are other extreme 
cases in which a 1 K. W. set has only been able to send 
a few miles. Again, the same set will be able to send to 
variable distances under other conditions and at differ- 
ent times. Thus, the transmission in winter is generally 



92 Experimental Wireless Stations 

better than during the summer. The transmission at 
night is generally nearly twice as good as during the day 
time. The transmission during f ayorable atmospheric 
conditions is from two to ten times greater than when 
carried out under unfavorable atmospheric conditions, 
and so on. In order to obtain data, the working distance 
under practical conditions and with efficient, well-adjusted 
sets is taken as a standard, and, of course, under favor- 
able conditions, this limit is often greatly exceeded. 

This standard transmission calls for a range of one 
mile for every ten watts of energy which is- used at the 
transmitting station. Thus, a y 2 K. W. (500 watts) set 
is expected to cover 50 miles, a 34 K. W. 25 miles, a 1 
K. W. 100 miles, and so on. The range for spark coils 
will be similar and should be reckoned on the watts used 
instead of the spark length alone. 

If the set is operated under very favorable conditions 
this limit will generally be exceeded, but, of course, if 
the adjustment or the instruments, or the natural condi- 
tions are poor, it is not likely that this limit can be at- 
tained. With this basis and the desired range known, 
the power required can be easily found. 

With a vacuum tube transmitter large distances can be 
covered with very small power. One- tenth of a watt per 
mile may be allowed if a sensitive receiving set with 
vacuum tube amplifier is employed. Radio-telephony 
has been carried out over a range of one hundred miles 
using aeroplane vacuum tube stations of small power. 

This done, the question is limited to the immediate 
selection of the type and size of transformer or spark 
coil to be used. Since a transformer requires a source 



Eange of Transmission 93 

of alternating current such as a lighting circuit and since 
this method is simpler and more satisfactory for experi- 
mental purposes, it should be adopted whenever possible. 
Transformers may be had in the market at a figure which 
can scarcely be duplicated by the experimenter, even if 
his own time is not considered, and the same may.be said 
of spark coils. The construction of such apparatus, of 
course, affords considerable education and satisfaction, 
but as regards the expense, little or no gain may be ex- 
pected. Very often, good second-hand coils and trans- 
formers may be had for little or nothing. Discarded 
automobile spark coils are easily obtained at garages for 
a mere song and are satisfactory for short distances. 

There are two general types of transformers, the open 
and closed core types. The former, while less efficient 
from the electrical standpoint is more efficient for wire- 
less purposes than the ordinary closed core transformer. 
The latter type, to be of the greatest use for wireless pur- 
poses, must be specially designed. In wireless transmis- 
sion the secondary of the transformer is largely on open 
circuit and the conditions are different than the ordinary 
transformer loads. For the maximum results, it is neces- 
sary to apportion the primary and secondary inductance 
and the mutual inductance properly, just as it is necessary 
to bring the, condenser and antenna circuits into reso- 
nance. Almost any high tension transformer or spark coil 
will do, but special designs are necessary when efficiency 
is desired. In the ordinary transformer, the load on the 
secondary increases in practically a direct ratio with the 
current input, while in a wireless station the load is es- 
sentially a condenser. This condenser reaches a maxi- 



94 Experimental Wireless Stations 

mum charge only when the constants of the transformer 
bear a resonant relation to the capacity of the condenser. 
When the resulting discharge causes a spark, the sec- 
ondary of the transformer becomes practically short cir- 
cuited so that the ordinary transformer would draw a 
greatly increased amount of power and an arc would be 
formed in the spark gap. Now this arc is very undesir- 
able since the condenser cannot be properly charged while 
it lasts and as a result an ordinary transformer cannot 
produce good oscillations. 

The wireless transformer, then, must be designed to 
draw a comparatively small amount of power when the 
condenser discharges and short-circuits the secondary 
winding, so that the spark will extinguish just as soon as 
the condenser has been discharged. 

In practice this may be attained by using an auxiliary 
adjustable resistance or reactance in the primary circuit 
of an ordinary transformer, or an adjustable inductance 
in series with the secondary of a closed core transformer, 
or else by combining this principle in the transformer 
itself. With the open core type of transformer, an ad- 
justable inductance in the primary circuit becomes essen- 
tial, and this method also allows of considerable flexibility 
in bringing the transformer into resonance with different 
capacities in the condenser circuit. Wireless transform- 
ers generally have several adjustments which allow the 
power input to be varied so that a corresponding change 
may be made in the condenser capacity without throwing 
the circuit out of resonance. In practice, it is common to 
rely upon the instinct of the operator to adjust the 
amount of capacity and power input to the right point as 



Range of Transmission 95 

indicated by the appearance of the resulting spark dis- 
charge. The main point is that the spark in the gap 
should not form an arc. With spark coils this method 
must be largely used since an accurate calculation of the 
required capacity is difficult. Spark coils should only be 
used when alternating current is not available. Either 
batteries or a D. C. generator may be used to operate 
spark coils and while they may be operated on no volts 
A. C. in connection with an electrolytic interrupter, this 
method is not very desirable. Data for wireless trans- 
formers and spark coils will be found in Chapter VII. 
The auxiliary primary apparatus such as keys, kickback 
preventers, and other items will also be considered later 
since their design depends largely on the amount of power 
used. 

After the power and source of power to be used have 
been decided upon, the proper amount of capacity to be 
used should receive attention next. This item depends 
on several quantities, which may be listed as : 

i. The power supplied to. the condenser. (Watts.) 

2. The frequency, or number of sparks per second. 

3. The secondary discharge voltage. 

In the case of an alternating current transformer, the 
transformer supplies an amount of power to the con- 
denser which may be represented by P kilowatts. If the 
condenser and spark gap are arranged so that the con- 
denser charges to a sparking potential once each half- 
cycle, or the natural spark rate (twice the natural fre- 
quency, i.e., 120 times per second if the primary fre- 
quency is 60 cycles), 



96 Experimental Wireless Stations 

nCV 2 Kilowatts 

1,000 
in which P represents the power, n the frequency (as, 
for example, 60 cycles), C the capacity of the condenser 
in farads, and V the potential in volts to which the con- 
denser is charged at the time the spark begins. 

This formula may be simplified to the following form : 

1,000 x (Power in K. W.) ♦ 
C= 

nV 2 

Now, when the power, the number of cycles, and the 
voltage to which the condenser is to be charged, are 
known, the required capacity can easily be calculated from 
this formula. It will be evident that the higher the fre- 
quency, the less will be the needed capacity, so that for 
the same output, a smaller capacity may be used for 60 
cycles than for 25 cycles, and so on. 

For example, suppose that the power source and 
power conform to the following data after the desired 
transmission range has been decided as approximately 25 
miles. 

Transformer, J4 K. W., primary voltage no, fre- 
quency 60 cycles, secondary voltage 20,000.* Substitut- 
ing these values in the formula 

1,000x^4 1,000 x. 25 

60 x 20,000 x 20,000 60 x 400,000,000 

.25 
= .0000000105 approximately. 

25,060,000 

♦This example serves more for an illustration than as a 
typical case. 



Range of Transmission 97 

On account of the large unit represented by a farad, 
wireless capacities are invariably calculated and carried 
out in microfarads, a microfarad being i,ooo,oooth of a 
farad. To change this result to microfarads then, the 
answer is multiplied by 1,000,000, giving a result of .0105 
microfarads. 

This calculation is simple and sufficiently accurate for 
all ordinary purposes. When the construction of con- 
densers for transmitters is taken up, we shall see how the 
desired capacity can be w r orked out. 

It will be obvious from the formula that when a low 
potential is used, the capacity must be relatively large, 
and that if a high potential is used, the capacity will be 
correspondingly small. In practice the transformer used 
generally has a potential of from 15,000 volts for *4 an d 
J/2 K. W. to perhaps 30,000 or more for the larger sizes. 
However, there is no material gain in the amount of nec- 
essary dielectric material for a given amount of power, 
whether or not a high or low voltage is used since the 
small capacity for a high voltage is compensated by the 
corresponding increase in thickness which is necessary to 
withstand the increased voltage without breaking down. 
If the capacity is not properly designed, it is liable to 
break down, as well as act to reduce the transmitting 
efficiency. An incease in the frequency, then, is the only 
factor which will materially decrease the actual bulk of 
the condenser. Generally speaking, a high voltage within 
limits is advantageous for transmitting purposes because 
of the resulting transmitting efficiency, but this item 
should always be kept within limits and particularly so, 



98 Experimental Wireless Stations 

when small and only moderately insulated aerials and 
instruments are used. 

In estimating the voltage to substitute in the formula, 
15,000 volts to the centimeter of spark length is gener- 
ally allowed (1 inch being 2.54 centimeters), since this 
has been found the approximate value for a heated and 
ionized spark gap. 

TABLE OF CAPACITIES REQUIRED FOR 

CONDENSER CIRCUIT WHEN SPARK 

COILS ARE USED 

Length of spark in inches. Capacity in microfarads. 

x /i inch 001 

Y2 inch 002 

1 inch 004 

2 inches 008 

3 inches 012 

4 inches 016 

These values are approximate, but will vary according 
to the particular coil used. Spark coils for wireless pur- 
poses should be rated in watts instead of spark lengths. 

Now, with the condenser and transformer decided 
upon, the inductance for the primary or condenser circuit 
is the next item to work out. We have already seen how 
the wave length is varied by the amount of inductance 
and capacity in the circuit and since the capacity is prefer- 
ably a fixed value (wireless manufacturers making trans- 
formers generally supply a fixed condenser of the proper 
dimensions to begin with), the amount of inductance 
will decide the wave length in most cases. Indeed, when 



Calculation of Wave Lengths 99 

the condenser is properly calculated and constructed this 
method is the preferred standard. Before proceeding 
further, the method of determining- the wave length must 
Ee understood. This involves only simple mathematics 
and can be easily mastered by every reader, if it is not 
already familiar. A careful reading together with the 
working of a few problems is all that is necessary. 

CALCULATION OF WAVE LENGTHS 

The argument here applies to other forms of transmit- 
ters and to receivers also. 

The wave length is expressed in the metric system as 
a certain number of meters long. Now, feet can easily 
be changed into meters (sometimes written "Metres") 
by dividing the number of feet by 3.281 (1 meter being 
39.37 inches). 

The formula reads, 
Wave length (*) = v x 2ir ^L.C. 

(\) being a symbol for wave length, v the velocity of 
light in meters=3 x 100,000,000 in one second, L=the 
inductance in henry s, and C=the capacity in farads, n 
=3.1416. (.000001 farad=i microfarad., .000001 
henry=i microhenry). 

This formula can then be simplified as follows: 

Wave Length = 300,000,000 x 2 x 3.1416VL.C. = 
1,884,960,000 times the square foot of the product of L 
and C. or 1,884.96 times the square root of the product 
of L and C in microhenrys and microfarads respectively. 
Now, for a given wave length, the product of L and 
C will be a constant quantity, so that if the capacity C is 



100 Experimental Wireless Stations 

large, L will be small, or if the inductance L is large, C 
will be small. The quantity (LC) varies as the square 
of the wave length, so that if the wave length is to be 
doubled (LC) must be made four times as great, or if 
a given wave length is to be tripled, (LC) must' be made 
nine times its original value. 

In arc transmitters and some vacuum tube sending 
sets the value of L, the inductance, is usually much 
larger than C, the capacity, while in spark sets, a larger 
condenser capacity can be used. 

Now, in the formula there are three items to be rilled 
in by mathematical quantities. If any two are known, 
the value for the other one may be readily found. Thus, 
if a wave length of 200 meters is desired with the use of 
the .0105 microfarad condenser already calculated for 
the case taken as an illustration, the necessary inductance 
can be readily found. In order to still further simplify 
the formula so that it will not be necessary to extract the 
square foot of (LC) it may be expressed, 

Wave length V _ /LxC, expressed in henrys 
1,884,960,000/ and farads respectively. 

Using this formula, and expressing L and C in micro- 
henry s and microfarads respectively for this example, 



( 



(20P V T 
I =Lx.oio5 
1,884,960,000/ 

cancelling and dividing, 

i8.849,6oo#) 2#. 1st. 

9.4248 ) 1. ( .1061, quotient .... 2d. 
substituting this simplified value, 



Calculation of Wave Lengths 101 

(.1061 ) 2 =LxC=Lx. 0105 for the example taken 
that is, 

L — - OII2 57 = -011257 = 1.072 ap proximately. 

C .0105 

Thus, to obtain a wave length of 200 meters when the 
inductance is an unknown quantity and the capacity is 
.0105 microfarads, the formula gives 1.072 microhenrys 
as the proper amount of inductance. 

Now, this calculation is very simple, and may be used 
to find any of the values, wave length, capacity, or in- 
ductance, provided the other two are known. It applies 
to vacuum tube as well as other circuits. 

It might be well to memorize or jot down this for- 
mula in a convenient place, and if desired it may be 
remembered in the following form which applies to all 
cases which may arise. 



/Wave lengthV 
\i, 884,960,000/ 



Giving C in microfarads direct 
Giving L in microhenrys direct 



When the wave length is 200 this formula gives, 
L x C=.oii2$7, so that any inductance and capacity 
which will give a product of .011257 when expressed in 
microfarads and microhenrys respectively, will satisfy 
the equation and give a wave length of 200 meters. Now, 
since the condenser is worked out to correspond to the 
transformer used in each case, the required inductance 
can be found from the following for any case, the wave 
length remaining at 200 meters. 

— * .011257 /Giving L in microhenrys. \ 
C \C being in microfarads. / 



102 Experimental Wireless Stations 

It is believed that this set of formulas places the 
calculation of wave lengths within the reach of all the 
readers. 

When the construction of inductance is taken up, the 
matter of calculating the inductance so that the helixes 
and transformers are of the required design, will be 
taken up. 

The reader should have a pretty good idea of the 
relations of the circuits to each other by now, so that it 
will be evident that to use a high wave length of 1,500 
meters with a spark transmitter, the inductance must be 
nearly 50 times as great as for a wave length of 200 
meters with the same condenser, and aside from the item 
of decreased efficiency, the dimensions of the necessary 
inductance make it impracticable. Small experimental 
stations should, therefore, limit the wave length to the 
smaller value. This could be done with a vacuum tube 
transmitter if desired with good efficiency. 

SPARK GAP 

Before considering the secondary or antenna circuit, 
a few notes on the general requirements of the spark 
gap will be given. The length of the spark gap is gov- 
erned by the potential at the terminals, so that it must 
be increased as the potential at which the condenser is 
charged is increased, the other conditions being constant. 
The other dimensions, or the size of the faces of the spark 
electrodes, must be sufficient to conduct the energy with- 
out undue heating. These are the essential features of 
a gap and the exact size and shape admit of numerous 



Antenna Circuit 103 

variations. Suitable constructions for various types of 
gaps will be taken up in detail later. 

ANTENNA CIRCUIT 

The proper dimensions for the antenna circuit are 
obtained in much the same manner as for the condenser 
circuit, and both of the said circuits must be adjusted to 
very nearly the same wave length for the maximum re- 
sult. There is some difficulty in calculating the capacity 
and inductance of an antenna with any degree of accu- 
racy, since there are many elusive quantities which make 
up the total.* When the primary or condenser circuit is 
accurately calculated and adjusted, the antenna or sec- 
ondary circuit can probably be best adjusted to resonance 
with the primary circuit by means of a hot wire am- 
meter, wave meter, geissler tube, or miniature light bulb, 
and some of these methods will be taken up in detail 
later. 

The capacity of the antenna wires increases with the 
height, but not directly. It is nevertheless desirable to 
have the transmitting aerial as high up as is possible. 
The capacity of stranded wire is only a very little greater 
than that of a solid conductor having the same outside 
circumference. The capacity of a number of wires in 
close proximity is considerably less than the sum of the 
individual capacities. Solid metallic structures in space 
have only a very little greater capacity than ordinary 
wires, and a few small wires uniformly spaced have prac- 

* A ship's antenna capacity, for instance, is sometimes dif- 
ferent when in port than at sea. 



104 Experimental Wireless Stations 

tically as great a capacity as a solid sheet or tube occupy- 
ing a similar space. The use of sheets, netting, tubing, 
and the like is therefore not economical or desirable. 
Some battleships use twelve or more wires arranged in 
a circle as a cage conductor but this is done to decrease 
the resistance rather than to increase the capacity. The 
approximate inductance and capacity of aerial wires can 
be worked out by a complicated process, but since even 
this method admits of considerable error, these formulas 
are omitted. 

Perhaps the most simple and satisfactory method of 
apportioning the antenna conductors for a given set is as 
follows: Take three-fourths of the wave length in 
meters to find the wave length to be embodied in the an- 
tenna conductors. That is, make the natural wave length 
of the antenna approximately three-fourths of the total 
wave length. To do this, it is necessary to make the 
effective length of the aerial approximately .6 of the 
total wave length in meters, in feet. This is calculated by 
a process which is simple and of no direct interest, and 
to illustrate, — 

For a wave length of 200 meters, the effective length 
of the aerial should be .6 of 200 in feet, or 120 feet. (See 
Aerials.) This is only a rough approximation, however. 
For large wave lengths, this method is not recommended. 
When this rule is used, a margin of approximately one- 
fourth of the total wave length is left to the adjustment 
of the secondary portion of the oscillation transformer. 
In constructing the aerial itself, it is well to allow one 
No. 12 conductor or its equivalent in the antenna for 
every 100 watts of energy to be used, and to provide 



The Transmitter 105 

a minimum of two conductors even if only 30 watts 
are to be used. Thus, a / 2 K. W. set should have five 
antenna conductors at least, and so on. In fact the limit 
is soon reached so that it is impracticable to use more 
than three-fourths or one K. W. with a wave length of 
200 meters or less. For one K. W. and larger sets, a 
high wave length should be planned for. This will mean 
a considerable increase in the total expense, as everything 
is best enlarged accordingly. See Chapter XX for legal- 
requirements.) A J4 or J^ K. W. outfit is ideal for 
experimental purposes. 

We have now considered the main factors of the 
damped wave transmitting sets and station, and the de- 
tails as well as the calculations which apply to any type 
of station are ready for attention. In choosing a site 
for a station, a quiet place is to be preferred and this 
matter is particularly true of the operating room. The 
latter should be provided with good ventilation, sound, 
tight walls, and should have a total floor space of about 
125 square feet is possible, though less may be used. A 
corner of a workshop, laboratory, or similar place is 
suitable. 

Note: It should be remarked that the estimated range 
of one mile for every ten watts cannot usually be ex- 
pected over long distances with short aerials and wave 
lengths on account of the absorbtion of short waves. 

PERCENTAGE OF COUPLING 

By placing the wave meter in relation to the antenna cir- 
cuit and observing the length of the two radiated waves 
emitted by the usual spark transmitter the percentage of 



106 



Experimental Wireless Stations 



BUU3J.Uy Ul 
UOi4.aH I0SQ A6J3UJ Xjopuotes 



*-3lU/2 






k / 


/ 


if 






-£^ 




s?;s 










^ 


^«s 


^P 


ii-^ 


*x-£; 




II 




VJ> \ 







A Complete Transmitter 107 

coupling between the primary and the antenna circuits can 
be determined from the relation, 

o + * r Xj— Xj x 100. 

Percentage of coupling = — - r 

K + K 

Xa = longer wave 
X, = shorter wave 

EXAMPLE OF A COMPLETE SPARK TRANS- 
MITTER 

In Figure 31 the complete circuits for a quenched gap 
spark transmitter are shown. Usually a private station 
does not have a separate generator for a primary source 
nor a complete set of indicating instruments. This illus- 
tration, however, is worthy of attention for study pur- 
poses because it shows the essential relations of the 
circuits. 



CHAPTER VII 
Transformers and Spark Coils Construction Details 

Principle of Induction Coil; Transformer Construction Data; 
Building a Transformer; Reactance Coil; Spark Coil; 
Table for Various Spark Coils with Dimensions. 

Transformers for wireless purposes are relatively in- 
expensive and quite efficient. They are rated according 
to the power, as % K. W., J / 2 K. W., and so on. They 
can only be used when an alternating" current supply is 
available. For experimental purposes a transformer giv- 
ing a secondary potential of 15,000 or 20,000 volts and 
of Y± or y?. K. W. is recommended, preferably the for- 
mer. The reader is advised that it will probably cost 
as much to construct a suitable transformer as to buy it 
in the open market and that some skill is required in 
addition to the data here given if an efficient transformer 
is to be constructed. 

In its simplest form, a transformer is nothing more 
than two independent coils of wire wound around a com- 
mon iron core. An alternating current impressed upon 
one of the coils (the primary) causes a current to be 
generated in the other coil by mutual induction, although 
the two coils are insulated from each other and the core. 

108 



Transformers and Spark Coils 109 

The second coil is called the secondary and is generally 
wound for wireless purposes so that it has a large num- 
ber of turns. The voltage of the primary and the voltage 
of the secondary have a ratio corresponding to the rela- 
tive number of turns. Thus, if the primary has ioo 
turns and is supplied with a voltage of ioo and current 
of 10 amperes, (i K. W.), and the secondary has 50,000 
turns of wire, the secondary voltage will be 50,000, but 
the amperage will only be one-fiftieth of an ampere.* 

Now, there are many quantities to consider in designing 
a transformer, and a desired design can be nicely cal- 
culated. The matter in this chapter will be limited to 
the direct construction of designs which have already 
been worked out as suitable. 

The core is generally arranged in the form of a rect- 
angle and is made up of thin laminations of soft sheet 
iron, each lamination being coated on one side with var- 
nish for insulation. This is to prevent eddy current loss 
and is essential. The arrangement of the coils admits of 
many variations, but for simplicity of construction it is 
preferable to place the primary winding on one leg of 
the core and the secondary on an opposite leg. The flux 
leakage is somewhat greater than when the primary and 
secondary are evenly divided on the two cores, but the 
construction and particularly the insulation is facilitated 
by this method. The foremost requirement of wireless 
transformers is good insulation, and this item should 
receive particular attention in the construction. 

* This is taken without considering the core and copper 
losses. Good wireless transformers are about 90 per cent 
efficient. 



110 



Experimental Wireless Stations 



TABLE OF TRANSFORMER DATA 



Watts 


100 


250 


500 | 


750 | 


1000 | 


1500 


1 2000 


A 


9 


9V 2 


95/ 2 1 


9/ 2 i 


11 1 


12 


1 11 


B | 


6 l A 


7 


7 I 


IV* 1 


10 i 


10 


1 15 


C I 


VA 1 


m I 


m 1 


Wa \ 


2 1 


VA 


1 2V2 


D 


16 


12 


14 I 


13 I 


6 | 


5 


I 4 


E 


5 


5/ 2 


V/ 2 1 


VA 1 


654 I 


854 


!' 854 


F | 


3/16 | 


54 


Va 1 


54 1 


54 


Va 


1 54 


G 






Em] 


3ire Cloth 






H 


1 16 


1 16 


14 ! 


14 I 


12 


10 


1 8 




D.C.C. 


D.C.C. 


D.C.C.I D.C.C 


D.C.C.I D.C.C. 


1 D.C.C 


J 1 


3*/ 2 


4 


5^ I 


6 I 


7 


10 


1 14 


K 


8 


9 


9 I 


10 1 


18 


22 


| 23 


L 




34 


t Enamel 




32 Enamel 


30 En'l 


M 


2V 2 


2V 2 


VA 1 


23/4 I 


5 


5 


9 


N 


V* 


V* 


V* I ** 54 54 Va 


, 


1 Va 


1 Va 


I 54 1 


54 I 


54 1 


54 


1 ■ 54 


P 


7 


7 


7 ! 


8 1 


10 


10 


1 16 


Q 


1 54 


1 Va 


1 54 1 


54 1 


54 


54 


1 54 


R 






Em Empire 


Cloth 







KEY TO TABLE 

A — Length of core (outside measurement). 

B — Width of core (outside measurement). 

C — Thickness of core. 

D — Number of primary layers. 

E — Width of secondary sections (each side). 

F — Thickness of insulation between core and primary. 

G — Kind of insulation between core and primary. 

H — Size (B and S) primary wire. 

J — Weight of primary wire. 

K — Approximate number of pounds secondary wire. 

L — Size (B and S) secondary wire. 

M — Length of windings. 

N — Thickness of separators for secondary sections. 

O — Thickness of sections in secondary. 

P — Number of sections in secondary. 

Q — Thickness of insulation between core and secondary. 

R — Kind of insulation between core and secondary. 



Constructional Details 



111 



The following data will be found useful in construct- 
ing* suitable transformers (closed core type), with out- 
puts which compare favorably with the inputs. The con- 
struction must be carefully carried out or the dimensions 
and sizes will not hold good. This data is for transfor- 
mers operating on 60 cycles at a voltage of 100 to 120, 
which is the current most in use. The cores are arranged 
in the form of a rectangle and the primary is placed on 
one leg while the secondary is placed on the other. These 
legs are denoted by the letter B in the table. The letter 
C denotes one side of the core. The core proper is 
square, so that when the thickness is given as 2 inches, it 
means that the core is 2?l2 inches. The separators (N) 
are of the proper size when fibre is used. 

CONSTRUCTIONAL DETAILS 

The core. Fig 32 shows the arrangement of a square 
core and details. The strips are best cut out by means 






Stagger 
Fig. 32. — Iron Core Transformer. Arrangement of Core. 



112 



Experimental Wireless Stations 



of square shears which may be found at any tinshop. 
When this type of core is used, it will be necessary to 
use an auxiliary primary inductance or reactance coil in 
order to compensate for the capacity and maintain 3 
high power factor. This type of transformer lacks suf- 
ficient inductance after the windings are in place, so the 
arrangement of Fig. 33 should be adopted if possible .* 




=s~- 






■ip 1 :: 

1 WgrihnaryUg 

VM 


^jS 










1 


■Illlllllll 11 :!!'' 1 "' 

m»- 





-Secondary Lea 



Fig. 33.— Transformer Core with Separate Tongue. 

This form of core gives rise to considerable magnetic 
leakage, causing an increase in the primary induc- 
tance, and makes the use of auxiliary inductance un- 
necessary. When the primary has insufficient inductance 
the spark forms an undesirable arc at the gap, so that 

* Extra iron must be allowed as the table is for plain cores. 



Constructional Details 113 

this is an important item. In some types of wireless 
transformers, this extra portion or tongue is made so 
that the air gap is adjustable, giving a close control of 
the current. This extra portion does not materially alter 
the dimensions given in the table, but extra iron must be 
allowed and calculated if this arrangement is adopted. 
Transformer iron may be had from supply houses cut 
to size, or a good grade of stovepipe iron may be used. 
The legs should be wound with a few layers of empire 
cloth. The core can be squared up by tapping it with 
a hammer or mallet. The secondary leg should be fur- 
ther insulated by additional turns of empire cloth, the 
number of which should be ample to take care of the 
estimated secondary voltage and a 50 per cent overload. 
No. 6 is a convenient size for the empire cloth and has 
an average puncture voltage of 7,800. A good way to 
find the desired number of turns is to use as many times 
the number of turns used for the primary leg as the 
number of secondary turns is times the number of 
primary turns, that is, the insulation is best proportioned 
according to the relative turns of the two windings. 

The Primary. Wind the primary evenly on the pri- 
mary leg, leaving some 6 or 10 inches at the ends of the 
wire for leads. Taps may be taken out towards the end, 
if different inputs are desired, in which case the number 
of primary turns should be slightly increased over the 
number given in the table. The winding is best done by 
hand on account of the heavy wire and should never ap- 
proach too near to the part of the core which forms a 
joint, or beyond the empire cloth, it being understood 
that the latter is kept within the limits of the leg proper. 



114 



Experimental Wireless Stations 



The completed winding can be covered with a few turns 
of empire cloth or tape. 

The Secondary. The sections are wound on a section 
former in a lathe or makeshift lathe. The arrangement 
of a section winder is shown in Fig. 34, and should be 
made in proportion to the size of the coil to be wound. 
This former should be made from iron, steel, or brass 
and not of wood, and is preferably made by a machinist 
so that the plates are true. The saw cuts (slots) are to 
allow threads to be passed around the completed section 
before it is removed. This round form is more con- 



-S/ofs 




Fig. 34. — Section Winder for Making Spark Coil Secondaries. 

venient than a square form, although the latter may be 
used. The resulting air space between the coil and core 
is no disadvantage since it acts as a cooling duct. The 
winding should be done slowly and evenly, avoiding 
kinks and breaks. A broken wire should be soldered. 
With a little practice this winding will not be difficult, 



Constructional Details 115 

and can be rapidly carried out. The section should be 
tightly wound and when completed, the threads should 
be passed around it and through .the slots to keep it in 
shape. Leave several inches at the beginning and end 
of the winding for connections. After it is bound, the 
section should be removed with care and placed into a 
pot or pan containing melted paraffin or a mixture of 
paraffin and beeswax. The latter should not be too hot 
since its insulating value is less if it is at too high a 
temperature. Let the section soak in the wax for some 
time until air bubbles cease to rise, then lift it out by 
means of a string or spoon. Place the section on a porce* 
lain plate and squeeze the excess wax out by pressing 
on the section from the top with another cold porcelain 
plate.* The other sections can be wound while the first 
few are being insulated, to save time. These sections 
can be taped with a strip cut from empire cloth if de* 
sired. The fibre separators can also be soaked in the wax 
mixture. Commercial coils are impregnated by the 
vacuum process. 

Assembling. The sections should be connected in 
series so that they form a consecutive winding with the 
connections made alternately at the middle and at the out- 
side. The joints should be soldered. Be sure that the 
sections are properly connected so that the direction of 
the winding is consecutive as otherwise one or more sec- 
tions will buck up against the rest. The sections should 
then be arranged on the core with the separators between 
them, and melted wax may be used to fill up the inter- 
vening space so that they will be rigidly in place on the 

* Glass may also be used. 



116 Experimental Wireless Stations 

core. It is good practice to divide the insulation between 
the sections into two parts so that the inner connection 
can be placed between two separators. The sections are 
best joined after they are arranged on the core. A num- 
ber of separators should be placed at each end of the 
completed winding and if possible a thick head should 
be provided as a flange for each end of the coil. 

The primary and secondary legs are now joined by 
the core pieces and squared up. The tongue of the 
tongue type is left alone for the present. In the tongue 
type, the primary core is placed at the tongue end. This 
tongue should be nicely bound by itself. The core is 
then clamped together and nicely squared up by means 
of strap or angle iron and bolts. 

The transformer can now be mounted in any suitable 
manner and the terminals brought out to suitable binding 
posts. The tongue is left in an adjustable position close 
to the core but insulated therefrom, so that its relative 
distance can be adjusted according to the amount of con- 
denser used across the secondary terminals. Tests should 
be made with a telephone receiver and battery for short 
circuits and breaks, and if any are found they must be 
located and repaired. It is well to cover the secondary 
with a number of layers of empire cloth. The other de- 
tails are left to the reader. 

REACTANCE COIL 

A suitable reactance coil for use with the transfor- 
mer when a plain core type is employed, may be con- 
structed by making a hollow coil of wire and sliding an 



Spark Coils 117 

iron core in or out of it according- to the desired adjust- 
ment. The core should be of sheet iron and of dimen- 
sions corresponding to the size of the primary leg of 
the transformer core. That is, if the primary leg is 
io inches long and 2^.2 inches, the core for the reactance 
should be this same size or a little larger. Now make a 
wooden or fibre frame about one-eighth or three-six- 
teenths of an inch thick with inside dimensions so that 
the iron core can slide freely in and out of it, and wind 
about two or three layers of wire on it. The wire should 
be a few sizes larger than the primary wire, if possible. 
Thus, if the primary wire is No. 12, No. 10 is suitable 
for the reactance coil. This reactance is connected in 
series with the primary winding and the adjustment is 
made by putting more or less of the iron core inside of 
the winding. 

It is believed that the foregoing will be sufficient work- 
ing directions to enable the reader to construct efficient 
transformers and reactances, providing that the work is 
carefully carried out. Many minor details have been 
omitted, and unless the reader has some experience, he 
will very likely find several little points which must be 
independently solved. The main requisite is again stated 
to be, INSULATION. 

Inasmuch as open core transformers are less efficient 
than closed core types and little if any easier or cheaper 
to construct, designs for this type are omitted. 

SPARK COILS 

A spark coil is similar to a transformer except that 
it has an open core and operates by means of an inter- 



118 



Experimental Wireless Stations 



TABLE FOR WIRELESS SPARK COILS 



(Size.) 


A. 


B. 


C. 


D. 


E. 


F. 


G. 


A in. 


5^ 


a 


CT 


1-16 in. 


20 


225 


Em. 


^in. 


5^ 


a 


CT 


1-16 in. 


20 


225 


Em. 


lin. 


Wa 


A 


Em 


2 


18 


170 


Em. 


2 in. 


7 


5 A 


Em 


2 


16 


184 


Em. 


3 in. 


8 


54 


Em 


2 


16 


208 


Em. 


4 in. 


stt 


i 


Em 


3 


16 


232 


Em. 


5 in. 


9A 


i 


Em 


3 


16 


256 


Em. 


6 in. 


10 


vA 


Em 


3 


14 


214 


Mi. 


8 in. 


14 


vA 


Em 


3 


14 


320 


Mi. 


10 in. 


24 


3 


Em 


4 


12 


400 


Mi. 


(Size.) 


H. 


I. 


J. 


K. 


L. 


M. 


N. 


A in. 


4 


38 


3oz. 


1 


m 


4^ 


250 


Kin. 


4 


38 


4 oz. 


1 


m 


vA 


300 


lin. 


6 


38 


541b. 


2 


154 


4K 


800 


2 in. 


6 


36* 


lib. 


2 


2% 


53/4 


1400 


3 in. 


8 


36* 


IK lb. 


2 


3 


6 


2000 


4 in. 


8 


36* 


2 lb. 


3 


4 


6 


2500 


5 in. 


8 


36* 


3 lb. 


3 


4K 


6 


3800 


6 in. 


^in. 


36* 


51b. 


4 


5 


ey 2 


6000 


8 in. 


M in. 


36* 


8 lb. 


8 


8 


7 


8500 


10 in. 


As in. 


28* 


121b. 


16 


11 


12 


10500 



IN THIS TABLE,— 

A — Length of Core in inches. 

B — Diameter of Core in inches. 

C — Insulation on Core — (CT. — Carboard tube, E. M. — Em- 
Cloth.) 

D — Thickness of insulation on core. 

(In layers, except l A inch and ^-inch sizes.) 

E— Size (B&S) Primary Wire (D. C. C.) 

F — Number Turns Primary Wire. 

G — Kind of insulating tube. 

(Em — Empire Cloth) (Mi — Micanite.) 

H — Thickness Isulating Tube. (Layers for Em. and inches 
for Mi.) 

I — Size (B&S) Secondary Wire. (* means Enameled.) 

J — No. Pounds Secondary Wire. 

K — No. Sections in Secondary. 

L — Approximate Diameter, Secondary. (In inches.) 

M — Distance between coil heads. (In inches.) 

N — Total No. Sq. In. of Foil in Condenser. 

Note : These coils use a medium speed vibrator. To use table, 
find length of spark wanted (Size) and read across, as A inch — 
5^— A— C T., etc., A inch— 4— 38— 3 oz., etc. 



Spark Coils 



119 



rupted current. These coils are preferably purchased, 
since they may be had almost as cheap as the materials 
for construction. However, for those who may wish to 
construct coils and who have some idea of the details, 
the following data for wireless coils are given. Wireless 
coils require a different design than ordinary spark coils. 
The sections may be wound as has already been de- 
scribed for transformer sections. The core in this kind 
of coil is made up of a bundle of straight soft iron wires, 



...- Secondary Terminals - ..^. 
to .- Secondary Sections, H 



.Insulation 
': (Primary 



Battery 



77777* t: n~ -Insulation Iron 



!?-» 



Iron Core 



■Vibrator 



■■ ""_':__"; ~ ,' ,.'.'... . . 



End Flanges 



Interrupter 
-Spring 



Condenser 



Fig. 35.— Induction Spark Coil. 

which may be had cut to size from supply houses. The 
other requirements, such as insulation, etc., are similar to 
those for transformers, and with the aid of the diagram 
of the relations of the circuits shown in Fig. 35, it is not 
thought that there will be any difficulty in carrying out 
the construction. The vibrator is best purchased from a 
supply house, since it is as cheap or cheaper than making 
one. The construction of the condenser is similar to the 



120 Experimental Wireless Stations 

construction used in receiving condensers, and the reader 
is referred to this heading for further instructions. 

A transformer is to be preferred and should be used 
whenever possible. The spark coil will operate satis- 
factorily on one or two six volt storage cells. A spark 
coil may also be used with an electrolytic interrupter on 
no volt A. C. or D. C. current. (See Chapter VIII.) 



CHAPTER VIII 
Auxiliary Apparatus 

Keys; Electrolytic Interrupter; Kickback Prevention; Aerial 
Switches; Automatic Antenna Switch; Storage Batteries. 



By using an electrolytic interrupter, a spark coil can 
be operated on 1 10 volts A. C. or D. C. The author finds 
i«*y s 




IIOV. 

■Reactance Coil. 




Hole 



FlG. 36. — Electrolytic Interrupter. 



that the interrupter shown in Fig. 36 is the most service- 
able for experimental purposes. This interrupter is very 

121 



122 Experimental Wireless Stations 

inexpensive and such common things as mason or other 
jars may be utilized. The electrodes are made of sheet 
lead. The electrolyte is made up by adding a little 
sulphuric acid to water, or else by adding some sal am- 
moniac to water. Other salts may also be used, but 
common table salt is not suitable. The proper amount 
is found by experiment. It is advisable to use the 
cooling jar as shown, as the interrupter heats rapidly 
when in use. The only difficulty in construction will 
probably be the hole in the glass or porcelain, or clay 
(glazed) jar. This may be readily bored with a new 
sharp twist drill, using turpentine as a lubricant. A 
glazed clay jar is the easiest to bore. The hole should 
not be too large, or too much current will pass. The 
following sizes for the holes are suitable. 

1-32 inch for coils giving up to ^2 inch spark. 

1-16 inch for coils giving up to 2 inch sparks. 

3-32 inch for coils giving up to 3 inch sparks. 

1-8 inch, largest size advised. This size allows from 
5 to 8 amperes to pass. 

In using the interrupter, the vibrator contacts of the 
coil must be screwed down tight as the vibrator is not 
needed. The interrupter is connected in series with the 
coil. (See Fig. 36.) The interruptions will be faster with 
the smaller size hole other conditions being the same, and 
they depend upon the fact that a gaseous insulating film 
is generated at the point of contact by the current which 
temporarily breaks the current. The interruptions or 
makes and breaks occur at a high rate of speed. The 
interruptions can be regulated to some extent by means 
of a variable inductance in series with it and the coil. 



Kickback Prevention 



123 



This may be constructed like the reactance coil described 
in Chapter VII. 

KICKBACK PREVENTION 

In using transformers or coils and interrupters con- 
nected to lighting circuits, the high tension currents often 
kick back into the line and cause considerable damage. 
The common effect of kickbacks are punctured meters, 
arcs in electric light fixtures, short circuits and blown 




Fig. 37. — Protecting Device for Lighting Circuit. 



fuses. In fact, whenever more than 200 watts are drawn 
from the line to operate a coil or transformer, steps 
should be taken to prevent kickbacks. An efficient triple 
preventer is shown in Fig. 37. The protection is three- 
fold, ground dissipators being provided in the form of 
condensers, high resistances, and minute gaps. These 
are all connected across the terminals of the line supply- 
ing current to the primary of the coil or transformer. 



124 Experimental Wireless Stations 

The gaps should be very carefully made so that they do 
not touch each other by a minute distance. The con- 
denser should have a large capacity and may be of the 
following dimensions or their equivalent. 

Each condenser has ten plates of 8xio glass * between 
which are sheets of tinfoil 6x8 inches alternately con- 
nected to form a capacity. This is constructed like any 
other condenser. 

The high resistance is attained by using graphite rods, 
each having about 1,000 ohms resistance, and should be 
of large diameter to dissipate the heat which is accumu- 
lated after a time. These rods are also connected directly 
across the line. The ground may be the regular 
ground of the station or else the lighting ground may be 
conveniently used. This arrangement will take care of 
kickbacks and will save the remainder of the circuits 
from damage. The. fuses shown are 6 amp. plug fuses, 
and should be promptly renewed if they blow. This 
protection may mean the difference between a serious 
fire and constant freedom from injury or trouble and 
should be adopted. The condenser cares for ordinary 
small charges, the gap for excessive charges, and the 
rods are an additional protection for the meter. The 
latter can be dispensed with if desired. Two incan- 
descent lamps in series may be substituted for the rods 
and will serve as an efficient protection. 

KEYS 

The key used for breaking the current into dots and 
dashes must handle considerable currents in most cases 

* Heavy paraffined paper can be used. 



Keys 



125 



and ordinary telegraph keys are only suited when a few 
watts are used, as with small spark coils. The reader 
can easily construct a heavy key along the lines of a 
telegraph key, using large pieces of zinc or two silver 



^Insulated ttand/es 
-Adjustable 




8ase-'' 
FlG. 38.— Ordinary Key Fitted with Large Contacts. 

dimes for contacts. An attachment for an ordinary tele- 
graph key which will handle large currents is shown in 
Fig. 38. The regular contacts are not used with this ar- 
rangement. A similar arrangement can easily be con- 



■Pivot 



Stop. 



-■Pivot 



^Spring 




FlG. 39. — Magnetically Operated Key. 

xucted. The arrangement is so simple that further 
comment seems unnecessary. The contacts can be of 
zinc or silver and should be of large surface. The aver- 
age telegraph key will have to be mounted on a separate 



126 



Experimental Wireless Stations 



base to use this arrangement. A similar set of contacts 
can be magnetically operated as shown in Fig. 39, in which 
case an ordinary telegraph or strap key can be used to 
close the circuit. This arrangement is advisable when 
currents in excess of 10 amperes must be handled. 
Springy metal can be substituted for the mercury. 

Another arrangement for handling large currents is 
shown in Fig. 40. Other arrangements for the same pur- 
pose are to connect a large condenser in shunt around 
the key contacts to absorb the spark, and to use oil about 
the contacts to prevent arcs from forming. The magnets 



Key Contacts 




Fig. 40.— Magnetic Blow-Out to Prevent Key Arcs. 



shown in the figure may be either single or double pole 
and of any suitable dimensions. The essential feature is 
that the poles* should be extended to the locality of the 
contacts, so that they can act to blow out arcs which form 
before the latter become of unwieldy proportions. Note 
the connections. Strap iron is suitable for the pole ex- 
tensions. 

AERIAL SWITCHES 
There are many forms of aerial switches, the object 



Aerial Switches 



127 



of which is to change from the sending to the receiving 
instruments. For small stations, an ordinary double or 
triple pole double throw switch can be used and connected 
as shown in Fig. 41. For large stations, either a big 
double or triple pole double throw switch can be used. 
The aerial switch is conveniently located, preferably at 
the point where the aerial leads enter the operating 



W 



^ 



D.P.D.T.Switch 



Sending 
Instruments 



Receiving 
Instruments 



Fig. 41. — Change Over Switch ; Sending to Receiving. 



room. A switch which allows of rapid change from 
sending to receiving instruments and vice versa is a de- 
sideratum, one type of such key being shown in Fig. 42. 
The details of construction are left to the reader, the 
essentials being that the contacts and switch pieces should 
be well insulated from each other, it being desirable to 
use hard rubber throughout. On account of the leverage 
it is only necessary to move the handle a short distance 



128 



Experimental Wireless Stations 



from the sending to the receiving position. The blades 
correspond to the radii of a circle in this type. 

AUTOMATIC AERIAL SWITCH 

This form is very much desired and used by experi- 
menters. It automatically disconnects the receiving set 
the instant that the key is used to send and as soon as the 




"Contacts? 



K Lever 
-Post 
Contact-^ 



Base 



Switch Blade, 



-4- 



K To Sender 
To Primary^ 



c=; 



To Receiver* 
/-Primary Switch 



Switch/ 
Blade \ 



•To Sender 



-Post 



,To Aerial 



^^\ 



-Ins u tat Ton 

To Receiver 
V- 



^Tb Ground 



,,-Post 



/■Lever 



J£_ 



Fig. 42. — Antenna Switch ; Rotary Type. 



Automatic Aerial Switch 



129 



message is sent, the receiving set is again ready to re- 
ceive. This particular embodiment is adapted to a closed 
circuit transmitter. The Figure 43 is self explanatory, 
and the reader will have little difficulty in making and 
attaching this arrangement to an ordinary key. German 



Receiving Position 




Form of Springs 

o 






To Coil 



Bushing 



Helix --> 
'Solder Connec tion Here 




Contacts on key Jg l±Z To *""'™9 Apparatus 
Fig. -43. — Break in Attachment Fitted to Key. 



silver or brass may be used for the springs and platinum 
is desirable for the contacts. The spring strips are in- 
sulated by hard rubber or fibre bushings and rubber 
tubing, the whole being clamped together by two brass 
machine screws. A short brass strip is used to attach the 
device firmly to the back end of the key lever. The 
springs must be adjusted so that the first two and the 



130 



Experimental Wireless Stations 



second two make contact when the key is up, and the 
second makes contact with the fourth when the key is 
down. This will be clear by referring to the diagram. 
Connections may be soldered to the lugs on the springs. 
Telephone switch parts may be used for a small power 
key only. 

AUTOMATIC SWITCH FOR HEAVY CUR- 
RENTS 

The foregoing switch is only suited to small stations. 
The one shown in Fig. 44 is adapted for heavy currents 




•.Contacts 



— Key Lever 

/Knob - , ' 
Contacts, 



flat, Thin.Silven Brass or Tin Springs, 
\ ,-Binding Posts -. \ 



db 



j: 



2 



Hard Rubber Sheeting '/s'Thicfc' 
I" Wide and?'/z"Lonq 



"Wide and2'/z"Longr 
Hard Rubber Piece- 1 ' 

Fig. 44. — Automatic Antenna Switch. 






Storage Batteries 131 

and is also suitable for an inductively coupled trans- 
mitter. The key is not materially different from the 
foregoing and can be readily constructed from the dia- 
gram. The object of these keys is to protect the receiv- 
ing detector from injury while sending and they operate 
through the sending inductance. This increases the 
wave length of the aerial for receiving to some extent, 
but is not harmful. This particular form is suited for 
both closed and inductively coupled transmitters 'or re- 
ceivers. As in the other arrangement, the hard rubber 
sheet is arranged on the key, being placed between the 
button and the key lever in this case. It is also sat- 
isfactory to mount the contacts on the back of the key 
on the adjustment screw. 

IN GENERAL 

The wiring in a wirelqss station should be carried out 
in accordance with the code requirements. A copy 
thereof may be had gratis by addressing the National 
Board of Fire Underwriters at either New York, Chi- 
cago or Boston. 

STORAGE BATTERIES 

In radio work storage batteries are used as an emer- 
gency auxiliary source for transmitters, for filament 
lighting and plate circuit feeders in vacuum tube circuits, 
and similar work. Suitable forms of the lead-acid or 
iron-nickel-alkali type are supplied by reliable makers 
with full directions for care and use. For information 



132 Experimental Wireless Stations 

on batteries see any good electrical or battery handbook 
or manufacturers catalogues. The main thing is to keep 
the batteries always charged according to directions and 
to use only pure water to replenish or special electrolyte 
supplied by the maker to refill the cells. 



CHAPTER IX 
Condensers and Capacities 

Condenser Theory; Calculation of Capacities; Dielectric 
Table; Building Condensers; Dimensions and Materials. 

A condenser (see Figure 45) is a device which stores 
energy and in its simplest form it consists of two coatings 
of tinfoil separated by an insulating substance, such as 
air, paper, glass, or oil, which is called a dielectric. The 
two coatings are insulated from each other as far as 
metallic connections are concerned and if they are 
charged by means of an induction coil or transformer 
they will discharge with a brilliant crackling spark when 
connected through a suitable gap. Now this discharge 
occurs so rapidly that it appears to be a single discharge, 
but it is in fact made up of a number of rapidly oscillat- 
ing discharges, first in one direction and then in another. 
During this process the polarity of the charge on the two 
coatings is rapidly reversed so that a given coating is first 
charged in one polarity and then in another at a high 
rate. The vibrations from the discharge are called oscil- 
lations and gradually die out with more or less rapidity 
according to the degree of damping. The spark gap 

133 



134 Experimental Wireless Stations 

causes damping because it offers resistance to the oscil- 
lating current. The time taken by an ordinary discharge 
is generally a small part of a second, but during this 
small space of time there may be as many as 100,000 to 
1,000,000 oscillations. 

Now the nature and amount of this charge depends 
on the dielectric rather than the coatings employed. It 
has been definitely established that the charge of a con- 
denser resides on the respective surfaces of the dielectric 
and not on the coatings or tinfoil. When a condenser is 
charged and the coatings removed, tests will show that 
they are not electrified to any appreciable extent, but if 
they are returned to position to form a complete con- 
denser with the same dielectric, they will form a highly 
charged condenser again. The dielectric of a condenser 
actually undergoes a strain and as in the case of mechan- 
ical strains, this results in heat after a time. 

The two coatings of a condenser are always charged 
oppositely, that is when one coat is charged positively, 
the other is charged negatively. These charges in oscil- 
lating back and forth travel at a speed of 300,000,000 
meters per second or the speed of light. When a con- 
denser is charged by a transformer, there are four stages 
as follows: 

1. First quarter cycle, condenser coatings are charged 
to the potential of the impressed E. M. F. 

2. E. M. F. decrease during the second quarter cycle 
so the charges on the coatings rush back to the trans- 
former. (A discharge occurs in the spark gap at this 
point, resulting in oscillations as has just been described.) 

3. Third quarter cycle. Same as the first quarter 



Calculation of Capacity 135 

cycle except that the direction and polarity of the charge 
is reversed. 

4. Fourth quarter cycle ; same as second quarter. A 
second discharge occurs in the gap. 

There are two discharges at the least for each cycle, 
or if the frequency of the transformer is 60 cycles there 
will be at least 120 discharges per second.* The higher 
the frequency of the impressed E. M. F. is, the greater 
will be the power of the circuit including the capacity, 
because of the increased rate of change of flux. In wire- 
less work, a capacity or condenser behaves in the fol- 
lowing definite manner: 

1. The apparent conductivity is directly proportional 
to the capacity and the frequency of the E. M. F. 

2. The apparent resistance or capacity reactance is 
inversely proportional to the capacity and the frequency 
of the E. M. F. 

We have already seen how the capacity in a transmit- 
ting circuit which is required for a given transformer 
may be found. All that remains then is to find the 
dimensions for a condenser which will give the required 
capacity. 

CALCULATION OF CAPACITY 

In order to standardize experimental apparatus, the 
parallel plate type of condenser is the best to adopt be- 
cause its capacity or a desired capacity can be readily 
calculated. The formula is, 

*A large number of discharges is obtained by interrupting 
the natural discharges with a rotary gap. See Chapter XL 



136 Experimental Wireless Stations 

k A 

C j- c. g. s. electrostatic units. 

4ir d 

in which, C represents the capacity, k, the dielectric con- 
stant, air or other gas at atmospheric pressure being 
practically I. Other values of k for different dielectrics 
will be found in the Table of Dielectrics. A represents 
the area of one of the plates overlapped by the other 
plate, and d is the distance apart of the plates in centi- 
meters. This formula is accurate only when the distance 
between the two plates is relatively small in comparison 
with the length and breadth of the plates. 
This may be expressed : 

KA 

C = -^TrS i-orC4 w Dx9Xio 5 =KA 

4 it Dxqxio 5 ^ y 

to express the capacity in microfarads. 

To find the desired area, this may be arranged, 

36. t DC x io 5 
A — K 

Now the quantity 36 pi x 100,000 is the same in every 
case, so the formula may be simplified to 

DCx 1 1309760, 

A = — and when glass is used for the 

K 
dielectric, which has a constant of 8 ; this may be further 

simplified to 

1 1309760 

A = DCx 1413720, because = 1413720. 

8 
So the calculation of the capacity and area for a given 

or desired condenser is really not difficult. The figures 
are in the metric system and to use in inches after the 



Calculation of Capacity 137 

area has been found in centimeters change in the follow- 
ing ratio : 

I inch=z 2.54 centimeters. I centimeter =.3937 in. 

1 square inch=6.45 sq. cm. 1 sq. cm.^.1550 sq. in. 

In order to illustrate the use of this formula, — suppose 
it is desired to find the necessary area for the tinfoil to 
make up a condenser of .002 microfarad, using glass .1 
centimeter thick. Ordinary glass plates are .05 inch thick 
or approximately .125 centimeter thick. Using the sim- 
plified formula, we get 

A=.i x .002 x 1413720=282.74 sq. cm. 

DIELECTRIC TABLE 
(K) Constants for, 
Air, empty space, or gases at atmospheric .pres- 
sure 1. 

Glass 6. to 10 

Light flint glass 6.5 

Dense flint glass 6.5 to 10 

Hard crown glass 7. 

Mica 6.6 to 7.5 

Hard rubber 2.7 

Kerosene oil 2. 

Castor oil 4.78 

Shellac 2.7 to 3.5 

Ebonite 2.5 to 3. 

Manilla paper 1.5 

Paraffin 1.75 to 2.3 

Resin 1.77 to 2.5 

Porcelain 4.38 

Water 80. 

Note, an average result is best to use in the formula. 
Glass should be taken as 7^ or 8 when ordinary glass or 
old photographic plates are to be used. The emulsion 
should be cleaned off before using the latter. 



138 Experimental Wireless Stations 

Now this surface can be apportioned in almost any- 
desired manner. For instance, three plates of glass of 
this size 12 by 14 centimeters and covered with tin foil on 
each side 9 by 10^ centimeters would be approximately 
right. 

To take another example, — desired capacity .02 micro- 
farad, using manilla paper .02 cm. thick, — what area of 
foil for A is required? 

Use the simplified general formula, 

DCx 1 1309760, 

A = — substituting 

K 

.02 x .02 x 1 1309760 4523.9 

A= : =- =3 OI 5-9 sq. cm. 

1.5 1.5 

This can also be proportioned as desired, about 30 
sheets of the dielectric being used. 

Almost any desired capacity can.be worked out to a 
close degree of accuracy in this manner. It will be noted 
from the formula that there are several factors which 
determine the capacity of a condenser, A, D, and K, so 
that if two are known, the third may be found. 

Now in designing a condenser for transmission pur- 
poses, the thickness of the dielectric must be sufficient to 
withstand the impressed voltage and an overload without 
puncturing. For this reason one centimeter to every 40,- 
000 volts should be allowed. Thus if the voltage is 10,000 
the dielectric should be made .25 centimeters thick and so 
on. However, if glass cannot be had in this size or a 
large enough size, two or more capacities of the same 
dimensions can be connected together, in series. This 



Structural Considerations 139 

method makes the use of ordinary thickness of glass pos- 
sible with high voltages, but since the capacity is thereby 
cut down, in approximately the same ratio, the capacity 
for each unit" must be correspondingly larger. Thus if a 
single unit is used which has a capacity of .2 microfarad, 
and if two condensers must be used in series to secure 
this same capacity without breaking down under the im- 
pressed voltage, each must have a capacity of .4 micro- 
farad. So that to increase the voltage which a condenser 
made up of a given size of plates may stand, by connect- 
ing units in series, to twice the voltage which a single unit 
can stand, each unit must have twice the capacity of a 
single unit if two are connected in series to give the 
capacity of the single unit. While we are on this subject, 
it is well to note that when condenser units are connected 
in parallel, the total capacity is the sum of the capacities 
of the condenser units, but the puncturing voltage which 
the parallel set can stand is limited to that of its weakest 
unit. For this reason the units used should be of iden- 
tical dimensions whenever possible. 

STRUCTURAL CONSIDERATIONS 

The condenser is an important part of the wireless 
station and unless properly constructed, the transmission 
efficiency will be materially affected. The main require- 
ments are, 

1. The foil used should be a good conductor and of 
sufficient size to carry the charges without undue heating. 
Copper is preferably used and may be had in thin sheets 
for this purpose. Tin foil should be heavy if used at all. 



140 Experimental Wireless Stations 

The kind used by florists is generally suitable. The high 
frequency currents require a large surface and if this is 
not provided, the conductor is likely to burn up. 

2. Radiation surface is necessary to dissipate the heat 
which is generated in the dielectric. When used in air, 
the condenser plates are generally spaced a short distance 
apart for this purpose, and when immersed in oil, the 
liquid acts as a cooling agent. Small condensers may be 
imbedded in paraffin or any good insulating compound. 

3. Contacts should be soldered to the tin or copper 
sheets forming the coatings to make the best contact pos- 
sible. The resistance of poor joints to high frequency 
currents is much greater than to low frequency currents. 
Stranded conductors make good leads to condensers. A 
common method of construction is to clamp projecting 
portions of the coatings tightly together to form a single 
conductor at the terminals. 

4. Brush discharges, surface leakage, and other losses 
should be minimized. This is accomplished by using a 
good grade of dielectric, allowing a safe margin around 
the coatings, making the coatings uniform and even, 
making the coatings fit the dielectric tightly, and placing 
the complete condenser in an insulator such as boiled 
linseed oil. 

5. Contacts should be as large as possible, to avoid 
undue resistance. 

The items under (4) are perhaps the most important 
and require careful attention. Some commercial con- 
densers have the coatings deposited directly on the glass 
dielectric. The first coat is silver and this is covered with 
electroplated copper. "Pyro" glass is used, as it stands 



Details 141 

heating. Plate condeners offer the most satisfactory 
solution to the several problems and in addition have the 
advantage already mentioned of being readily calculated 
for a given purpose. Plate condensers separated in air 
are not as desirable as those imbedded in an insulator 
because they tend to blister and aid brush discharges 
under overloads. For these reasons the standard type to 
be adopted, is the plate condenser made into convenient or 
desired units and imbedded in an insulator. 

DETAILS 

The glass used may be had cut to size at any hardware 
or paint supply house and for voltages over 15,000 the 
use of double strength glass is advisable. Data regard- 
ing the sizes, thickness and so on may be had from the 
dealer and is useful in calculating capacity and estimating 
material. Old photographic plates make very good con- 
denser dielectric material when *he emulsion is removed 
and may be had very cheap. The author once purchased 
two hundred 5x7 glass plates at 25c per hundred, and 
while the larger sizes are valued higher because of their 
use in picture frames, they may be had for a nominal 
sum. In fact, many photographers will gladly donate old 
glass plates if properly approached and told that they are 
for wireless experimental purposes. The emulsion can 
be removed by soaking the plates overnight in a strong 
solution of lye in water. Glass containing much lead is 
not suited for condensers, and all of the plates used 
should be of the same thickness throughout. 

Just before using, it is advisable to again clean the 



142 Experimental Wireless Stations 

plates with a rag dipped into alcohol, although warm 
water can be used if the plates are allowed to thoroughly- 
dry afterwards. The glass should be thoroughly clean 
and dry before using. 

MATERIAL FOR COATINGS 

Thin copper sheet or heavy tin foil should be used for 
the coatings and should be cut to size. If tin foil is 
used, it should be about No. 35 gauge if possible, and 
in any case it must be smoothed, by means of a print 
roller such as photographers use. In making con- 
densers which are so large that a single width of tin 
foil will not suffice, two or three strips overlapping each 
other can be used. The size of the coatings should be 
such that a margin of one inch is left on all sides rela- 
tive to the edge of the glass plate for every ten thousand 
volts to be used in the charging, though less may be 
used after a limit of two or three inches is reached, 
or when the plates are immersed in oil. 

ARRANGEMENT 

The arrangement of the plates and coatings is shown 
in Fig. 45. The lugs for the coatings are preferably in 
one piece with the coatings, but they may be separate 
pieces if they make good contact electrically with the 
coatings, and are mechanically strong. The latter 
method is less expensive as there is practically no waste 
of material. 

In soldering tin foil, the foil to which a strip is to be 



Material for Coatings 



143 



soldered must be laid upon a piece of copper or alumi- 
num sheet of some thickness, in order to conduct the 
heat away, else the foil will melt or burn up. When 
the condenser is to be used on high voltage, two or three 
thicknesses of the glass can be used between each sheet 
of foil to secure a greater disruptive strength, but the 







Fig. 45. — Condenser Details. 

capacity is of course correspondingly less and the total 
thickness of the plates between the two coatings must 
be used to calculate the capacity. 

The alternate lugs of the two coatings can be brought 
out on opposite sides of the plates or else suitably spaced 
on the same side. (See the figure.) It is a good plan 
to make the required condenser in several units, particu- 
larly if the capacity is large. Thus if twelve 8xio plates 



144 Experimental Wireless Stations 

are to be used, two units each having six plates are pre- 
ferable. This arrangement makes repairs from damages 
or punctures easier, since only one of the units is liable 
to be punctured at a time, while with a single unit, the 
whole condenser would be temporarily disabled. It is 
good practice to provide an extra unit or two if this 
method is adopted, in order to meet emergencies. 

BUILDING THE CONDENSER 

In building the condenser, lay a sheet of glass on a 
flat table, then place a sheet of foil with its lug on top 
of it, so that it lies flat and is evenly spaced from the 
edge of the plate. Now lay a second glass plate on top 
of this, and place a second sheet of foil on it, spaced 
as before, but arranged so that its lug comes either at 
the opposite side of the plate or suitably spaced from 
the first lug, as shown in the figure. Proceed as before, 
placing alternate sheets of glass and foil until all of 
the plates have been assembled. An extra plate should 
then be used to cover the top sheet of foil. When this 
IS done, the condenser will be a unit, with two sets of 
insulated plates alternately arranged. The unit can then 
be bound together by large rubber bands, rubber tape 
or string, or any suitable form of clamp may be used 
provided too much pressure is not applied. If the plates 
are pressed together too tightly the glass will crack, 
ruining the condenser. The two respective sets of lugs 
should now be firmly clamped between brass or copper 
sheet, or soldered together and to a large lead. Test 
the unit for short circuits with a battery and telephone 






Building the Condenser 145 

receiver, (the faint response does not indicate a short 
circuit, but is caused by the capacity of the plates). A 
few of the lugs can be left disconnected as shown at (c) 
Fig. 45, and separate leads attached to them so that the 
capacity of the condenser can be varied a little. This 
method is useful particularly with spark coils since the 
exact capacity needed is difficult to predetermine. 

The finished units should be placed in a suitable box 
or jar, (hard rubber or glass storage battery jars are 
excellent containers for this purpose), a hard rubber 
cover provided, connections brought to binding posts, 
and so on as desired. The jar or container should be 
liquid proof and should be filled with a good quality of 
transformer oil, boiled linseed oil, castor oil, vaseline, 
paraffin oil, or other non-explosive insulating oil. The 
condenser should be mounted or arranged in the jar so 
that it does not rattle and if the condenser is to be 
moved very much a thick insulator like vaseline should 
be used, so that the oil will not be continually running 
over and leaking. A good grade of lubricating oil can 
be used, the non-carbonizing oils used in automobiles 
being suitable and quite cheap. Oils which ignite easily 
or which carbonize or deteriorate quickly, as well as 
those which are poor insulators should not be used, 
since the function of the oil is to prevent leakage and 
brush discharges as well as to dissipate the heat caused 
by the hysteresis of the glass dielectric. 

MAKESHIFT CONDENSERS 

A condenser is really a very simple piece of apparatus, 
but too much care cannot be taken in constructing it if 



146 Experimental Wireless Stations 

efficiency is desired. For experimental purposes, old 
bottles, placed in a dishpan containing salt water, and 
filled two-thirds full with a solution of common salt and 
water can be impressed into service as a condenser, con- 
nections being made to the dishpan and to wires enter- 
ing into the bottles respectively. A large capacity is 
possible by this makeshift arrangement, but the capacity 
can of course not be accurately determined. Two rub- 
ber covered wires twisted together but insulated at the 
ends will form a condenser when connected about the 
secondary terminals of a small coil. There are other 
suitable forms for condensers, but since the type de- 
scribed is equal or superior to them and serves for all 
experimental purposes, these will not be described. 

By using copper, zinc, or even tin sheets (iron coated 
with tin), of some thickness between glass plates, a vari- 
able condenser may be made. The capacity can be varied 
by moving the plates forming one set of coatings in or 
out of the vicinity of the glass plates and the other set 
of coatings, thus increasing or diminishing the capacity. 
The construction of such an arrangement is very simple 
and the details need no further comment. The diagram 
of this arrangement is shown in Fig. 45 (d). It should 
be noted that this arrangement is just like an ordinary 
glass plate condenser except that rigid movable plates 
are substituted for the tin foil in one of the sets of 
coatings. In Fig. 45, (e) shows the manner of connect- 
ing condensers in parallel to increase the capacity, (f) 
shows the connections for series to decrease the capa- 
city, and (g) shows a combination of the two, which 
decreases the capacity. Taking a single unit for 



Sandwich Condenser Capacity 147 

comparison, the units being" of the same size (e) will 
give double the capacity, (f) one-half the capacity, 
and (g) an equal capacity, but using four units. 
The series and series multiple connections are used 
when the voltage impressed on a single unit is more 
than it can stand without puncturing, (h) Fig. 45 shows 
the method used to connect both a fixed and a variable 
condenser having the same form and size of dielectric 
in circuit. This method allows the exact capacity needed 
for a given transformer to be used. With this arrange- 
ment, the variable condenser need not have a very large 
capacity by itself since it is needed only to make up a 
small difference in most cases. 

SANDWICH CONDENSER CAPACITY 

For the condenser having N similar plates sand- 
wiched in between dielectric sheets with alternate plates 
Connected in parallel, the capacity is 

.0885 K(N— i)S microfarad. 

C = 

d( 1,000,000) 

K is the dielectric constant (1, for air). 

S is the area of one plate in square centimeters. 

d is the dielectric thickness in centimeters. 



CHAPTER X 
Inductances 

Calculation of Inductance; Construction of Helix and . Os- 
cillation Transformer; Simple Formulas for Definite Low 
Wave Length Sets. 

Like the calculation of wave length and capacity,* the 
calculation of inductance is quite simple provided the 
following- formulas are used. The answer is of course 
only approximately correct, but this is quite accurate 
and may be used directly in supplying the proper in- 
ductance in the transmitting circuit. The calculation 
for self inductance takes into account the magnetic 
circuit of the coil and the number of turns of wire in 
the coil. Any change in the shape or size of a coil 
will alter the inductance and special shapes require spe- 
cial formulas. The following relation holds good, how- 
ever, for cylindrical coils of one layer, as helixes or 
choke coils, and takes into account variable factors. 

(i) (5xDx;) 2 

= inductance in centimeters. 

M + 1/3 D 
In this formula, 

* Bulletin No. 74 of the Bureau of Standards may be had 
for 60c from the Supt. of Documents, Wash., D. G, and con- 
tains excellent radio information for the advanced reader on 
measurements and calculations. 

148 



Inductances 149 

D is the diameter of the coil in inches. 

T is the total number of turns of wire. 

M is the length of the coil in inches. 

The result is expressed in centimeters, which may be 
changed into microhenrys by dividing the result by 
1,000. 

To illustrate the use of this formula, find the induct- 
ance of a coil nine inches in diameter, io inches long 
and having io turns of wire. 

(5 X 9 X IO) 2 _ 450 2 _ 202 > 5QO 

10+ Yz of 9 13 13 

or 15,580 cm. approximately, or 15.580 microhenrys. 

Another formula which may be used to find the in- 
ductance of a helix in C. G. S. units is, 

(2) Inductance (L) = 1 (3.1416 dn), 2 where 

1, is the length of the helix, d its diameter, and n the 
number of turns per unit length. Thus with this form- 
ula, a helix 5 cm. in diameter, 50 cm. long and having 2 
turns to each cm., has an inductance of 

50 (3.1416x5 x2) 2 =50,ooo C. G. S. 

1 henry is equal to 1,000,000,000 C. G. S. electromag- 
netic units. 

To calculate the inductance of flat or doughnut helixes 
or coils (those having several layers wound over each 
other), the formula to use is, 

(3) 

(5xDxT) 2 



1/3D + 3/2M + 5/4N 
in which 



= inductance in cms., 



150 Experimental, Wireless Stations 

D is the average diameter of the coil in inches. 

M is the length of the coil in inches. 

N is the depth of the coil in inches. 

T is the total number of turns of the coil. 

To illustrate : Given a flat type of helix of the fol- 
lowing dimensions, calculate the inductance. 6 turns of 
copper strip I in. apart, depth of winding 6 in. Width 
of strip is i in. and average diameter 12 inches. (Inside 
6 in., outside 18 in.) 

(5xi2x6) 2 (360) 2 129,600 or 9970 cm. 

or 9.97 microhenrys. 
MUTUAL INDUCTANCE 

In oscillation transformers, mutual induction must be 
considered. When the transformer is a long single layer 
coil having a lumped secondary wound about it, the 
formula is, 

(4) 1^=4x3.1416 nNA. C.G.S. units. 

M is the mutual inductance, n the number of turns per 
cm. on the primary coil, N the total number of turns on 
the secondary coil, and A represents the area of cross 
section included within the primary coil. The length is 
to be measured in centimeters. 

1 henry is equal to 1,000,000,000 C. G. S. electromag- 
netic units. 

1 microhenry is one millionth of a henry. 

CONSTRUCTION OF A STANDARD HELIX 

For small stations in locations not likely to cause in- 
terferences the helix is perhaps better suited than the 



Construction of a Standard Helix 



151 



oscillation transformer and since it is easier to calculate 
and construct, it will be described first. The arrange- 
ment and details of the helix are shown in Fig. 46. The 
heads may be cut out of hardwood on a bandsaw or else 
turned out in a lathe, and should be eight inches in 
diameter and preferably ^4 of an inch thick. These 
heads are separated at a distance of 7 inches by four 
evenly spaced pieces, each y^ of an inch thick by 1 inch 




F3J 



Fig. 46.— Helix or Transmitting Loading Coil. 

wide by 914 inches long. These pieces should be 
smoothly finished. While the wire will stay on these 
pieces without artificial support, it is advisable to cut 
notches in these pieces to receive the wire. If possible, 
the outer surface of the pieces should be veneered with 
strips of hard rubber or fibre as extra insulation so 
that the wire does not make direct contact with the 



152 Experimental Wireless Stations 

wood. The separating strips are arranged as shown 
so that they form legs ^4 of an inch high at the bottom. 
The construction is quite simple, and if possible insu- 
lators should be substituted for the wood legs, in which 
case, the upright pieces will be made ^ of an inch 
shorter. The frame may be fastened together by screws 
and glue and should set true. The wire used is No. 4 B&S 
brass, aluminum or copper, and should be purchased al- 
ready coiled to approximately 9 inches in diameter or a 
little less. When wound, the wire will have a diameter 
of 10 inches and if of smaller diameter to begin with will 
stay tight. The wire is wound on the notches, so that 
the turns are spaced ^4 of an inch apart in an even wind- 
ing. Seven complete turns are required so that about 
19^2 feet of wire are necessary. This wire can be had 
at supply houses or hardware stores. The wire turns 
will start and end just a little less than one inch from 
each head, and the ends can be fastened down by large 
screw binding posts. The turns should be kept ^ of an 
inch apart and 10 inches in diameter for the purpose of 
standardization. This arrangement will be most suited 
for the low wave lengths and will give fairly sharp tun- 
ing. If the turns are made larger in diameter, the tuning 
will be less definite, and if more turns are used the wave 
length is of course increased. However, if the inductance 
is made too large for the aerial, the period and the radia- 
tion are cut down. Small aerials must naturally have 
relatively small helixes to maintain the necessary bal- 
ance. Flexible contacts or helix clips should be provided, 
as shown. Almost any desired size of inductance may 
be constructed along these same lines, and this standard 



Standard Oscillation Transformer 153 

is recommended for stations up to I K. W. using the low- 
standard wave length and located remotely from govern- 
ment stations. 

This helix has a maximum inductance of approximately 
14.28 microhenry s. One complete turn has an inductance 
of .291 microhenry. To find the inductance approxi- 
mately for any number of turns, multiply .291 by the 
square of the number of turns. Thus for three turns, 
multiply .291 by 9, for 3*^ turns, by 12*4, and so on. 

In practice, from one to three turns will be needed 
in the condenser circuit, according to the capacity of the 
condenser used, and while all of the seven turns may 
never be needed, the aerial circuit will generally include 
at least four or five turns, depending upon its dimensions. 

Copper or brass ribbon or coiled strip is also suitable 
for helix construction. 

STANDARD OSCILLATION TRANSFORMER 

The type to be adopted is the flat pancake form. The 
mutual inductance is readily adjustable with this type, 
and every part of the inductances can be readily reached. 
This transformer allows of very sharp and accurate tun- 
ing and is recommended for all stations using over 100 
watts of energy. It will also be useful to smaller sta- 
tions. Brass ribbon J4 inch wide is used in constructing 
both the primary and secondary and should be about 1-16 
of an inch thick. This may be had at hardware stores. 
About 40 or 42 feet will be needed. Thinner ribbon «may 
be used double or triple to make up the desired thickness. 

Obtain four strips of rubber or fibre Ya^Vz by 1^/2 
inches long. These should be straight and smooth. Hard- 



154 



Experimental Wireless Stations 



wood may be substituted. These should be joined as 
shown in Fig. 47, with half joints at the center to form 
two sets of crossed pieces. Before gluing the joints the 
pieces should be taken apart, marked and cut as shown. 
The slots are best cut with a hacksaw or band saw ; each 
slot being 1-16 of an inch wide and 3-8 of an inch deep. 
The slots are placed exactly y?. in. apart and begin Y\ of 
an inch from the end. Mark numbers 1 to 4 on the ends 



Cross Pieces 



A of jus table A djustable 




Secondary 
'S/ofs [ 

Base. 



~K 



Switch Clip 



"ins u fated 
Knob 



Fig. 47. — Oscillation Transformer. 



of the strips as shown in the figure so that when the 
two pieces are put together again the outside ends will 
be in order. 

The slots are laid off beginning from the outside so 
that each slot is one-eighth of an inch closer to the center 
than the one before, the slots thus forming a spiral when 
the pieces are placed together. Proceed the same for both 
sets of cross pieces, except that slots for five turns are 
provided for the set which is to support the primary 
while the other set is slotted for nine turns, thus coming 
nearer the center. After the slotting is done, fasten the 
pieces at the joints and bore a hole three-eighths of an 



Standard Oscillation Transformer 155 

inch in diameter through each set exactly at the center. 
Now fasten the two cross pieces down in a convenient 
place by means of one or two screws at the center hole 
and wind the ribbon in the slots. The ribbon should 
be either pressed or driven into the slots with a mallet. 
It is a good plan to begin at the inside to do this, taking 
care to make the curve of the spiral as uniform as pos- 
sible. Both forms should be wound in this manner, the 
ends of the ribbon being cut and smoothed off. The 
projecting ends should be sent slightly away from the 
adjacent turn of the ribbon. The ribbon should fit snugly 
in the slots so that it will stay in place indefinitely. The 
curve of the ribbon should not be too sharp at the sup- 
port points, but should form a gradual symmetrical spiral. 
The completed coils may be mounted in a number of 
ways, suitable supports being shown at (c) and (d) of 
the figure. In the latter case, the primary is movable 
axially as well as longitudinally with respect to the sec- 
ondary, this radial effect being useful in tuning very 
sharply. The details of mounting may be varied to suit 
the individual case, a threaded metallic rod, three-eighths 
of an inch through which the cross arms may pass and 
be fastened at an adjustable distance being suitable. The 
clip shown in the figure is made from an old 10 or 15 
ampere switch contact. An electrose or hard rubber han- 
dle is screwed on its base end. Four of these should be 
used, two each for the two coils. Similar pieces may be 
easily made for the clips if an old switch is not obtainable, 
almost any piece which will make good contact with the 
ribbon being suitable. 

The inductance of the primary may be calculated ap- 



156 Experimental Wireless Stations 

proximately for each turn, beginning with the center by 
using formula (3), taking first one turn, then the first 
two, then the first three, as though they were independent 
coils. Or if the inductance of each turn beginning with 
the outside is desired, a similar method may be employed. 
The inductance for the several turns is not constant on 
account of the difference in diameter between each turn. 
The values for the turns, beginning with the outside turn, 
are approximately: 

First turn, .868 microhenry. 

Two turns, 3.96 microhenry s. 

Three turns, 5.7 microhenrys. 

Four turns, 10.245 microhenrys. 

Five turns (maximum inductance), 13.5 microhenrys. 

When the coils are mounted to form a radial trans- 
former, the secondary should not be turned out of a 
parallel plane unless very sharp tuning is required. The 
tuning is sharper, within limits, the greater the distance 
between the two coils, but for ordinary purposes they 
should not be too far apart because the intensity of the 
transmitted signal is considerably less with a very loose 
coupling. 

The secondary inductance may be similarly calculated, 
although this is not necessary, since after the primary or 
condenser circuit is tuned to a desired wave length, the 
antenna circuit can be brought into resonance with it by 
connecting a number of turns in the aerial circuit which 
experiment shows to be right. 

A LOADING COIL 

A loading coil for the purpose of securing a high wave 



A Loading Coil 157 

length for experimental purposes may be constructed 
like a helix and inserted in series with the aerial circuit, 
as has already been explained. This loading coil need 
not have quite as large wire as the sending helix, al- 
though this size is a desirable standard in order to avoid 
undue resistance. No. 8 is a common size for this pur- 
pose. The loading must not be carried out too far with 
a given aerial, for after the ohmic resistance exceeds 
the square root of four times the inductance in henries, 
divided by the capacity in microfarads, the oscillations 
cannot take place. Any resistance impedes the oscilla- 
tions considerably. If the long wave lengths are desired, 
a large aerial capacity must therefore be provided to 
begin with, if efficiency is desired. A small aerial, how- 
ever, may be loaded for experiments. 

Almost any circular coil of wire can be made to serve 
as a helix or loading coil as a makeshift arrangement, 
but the reader is advised to adopt standardized instru- 
ments to make definite wave lengths, capacities, induc- 
tances, and adjustments possible. Sharp, scientific tuning 
can be attained in practically no other way. The best 
is not much harder to make than the other kinds and is 
well worth the time taken. 



CHAPTER XI 
Spark Gaps 

Purpose of Gap; Materials Suitable; Series Gap; Rotary Gap; 
Construction of Rotary Gap; Rotary Quenched Gap; 
Rotary Gap Circuits; Chaffee Gap; Two Tone Gap. 

A spark gap is inserted in the condenser circuit to 
allow the condenser to be discharged through it until the 
oscillations die out, and also to prevent the condenser 
from discharging until it is fully and properly charged. 
A spark gap, then, should be a good insulator while the 
condenser is charging and a good conductor while it is 
discharging. Now the resistance of the spark gap is one 
of the main factors which determine the damping of the 
oscillations, and unless properly constructed, considerable 
energy is wasted as heat in this part of the condenser 
circuit. The use of the proper amount of capacity in the 
condenser aids materially in keeping the length of the 
gap within efficient limits. Too long a gap causes an 
irregular stringy spark while too short a gap for the given 
condenser causes a wasteful arc to form in the gap. The 
gap should, therefore, be of adjustable length, able to 
conduct the energy without undue heating, and to make 

158 



Spark Gaps 



159 



and break as an insulator and conductor with rapidity. 
A poorly constructed or poorly adjusted gap can cut down 
the efficiency of transmission materially. Three types 
of gaps suitable for experiments are to be described, a 
common gap for small stations, a series gap for some- 
what larger stations, and a rotary gap. The quenched 
spark system will be discussed in a later chapter. 

A simple gap is shown in Fig. 48. The electrodes may 
be mounted in almost any suitable manner, care being 
taken to keep the two parts well insulated from each 



Ewith Flange 




Fig. 48. — Spark Gap. 



other and from other bodies. Either a vertical or hori- 
zontal mounting can be used and if desired, only one of 
the electrodes need be adjustable. The construction is 
quite simple and further comment seems unnecessary. 
The insulation used is preferably hard rubber throughout, 
though other materials may be substituted. The parts 
are preferably made of brass and the electrodes from 



160 



Experimental Wireless Stations 



zinc or an alloy of zinc with 2 per cent aluminum.* These 
electrodes should be made removable, as they pit after 
a time, and should be perfectly true. It is well to pur- 
chase these parts or have them made by a machinist, 
if no lathe is available. The electrodes should have plenty 
of surface, a diameter of ]/\ inch for every hundred watts 
being suitable. If this type of gap is used with large 
power, metallic radiating flanges should be provided to 
take care of the heat. The handle should be well insu- 



,,-;Co[3per 
,-;'Face Holes /*'>' Disks 



Si ,-Ad jus table 
J Handle 




Fig. 49. — Series Gap. 

lated so that the adjustment can be made while the coil 
or transformer is in operation. This form of gap can 
easily be muffled by placing a large glass jar over it, thus 
excluding the noise, or can be cooled by allowing a small 
fan to blow on to it, if desired. 

A series gap is shown in Fig. 49, which gives a smooth 
spark with many desirable features. It can readily be 
constructed in a desired size by referring to the figure. 
Too much care cannot be taken to insulate the electrodes 
well, and to provide large, true surfaces on the gap elec- 
trodes. While only a single dead electrode is shown in 
the figure, two or more dead electrodes may be used if 

♦Tungsten metal can also be used if obtainable. 



Spark Gaps 



161 



the sending coil or transformer is large. The electrode 
faces are made preferably of copper sheet, with perfora- 
tions as shown to prevent uneven wear and made detach- 
able as shown so that they can be cleaned or renewed. 
This type of gap has a large cooling surface and is to 
be commended for experimental use. The relative dis- 



Rotary Electrode 




Stationary Electrodes' 
Rotary j 
"Electrodes*'' 



Motor 



Side View 
■Shaft 



o 



Block 



Insulators 
Bearing--- 



,-Base 



Ssl 



Stationary ,/ 
/Electrode-''' 

' 3. i 



■■Post 



Top 
Vi«w 



Stationary.' 
2 Electrode 



Fig. 50. — Rotary Gap. 



tances of the electrodes should be adjustable, but each 
part of the gap should be of uniform length. The total 
length of all the gaps should be about the same as would 
be used in a single gap. 

The rotary spark gap is perhaps the most desirable 
of all the open discharge gaps and should be adopted 



162 Experimental Wireless Stations 

whenever possible. Its advantages are many, among 
which may be mentioned its high spark frequency, (the 
discharge spark is broken up into a series of uniform 
sparks, which increase the effective transmission range), 
the well cooled electrodes and the uniform sparks. 
There are many types and constructions for rotary gaps 
and while some of these are quite complicated, the reader 
will have little difficulty in constructing an efficient in- 
expensive gap. A suitable construction is shown in Fig. 
50. Other designs are also suitable. While numerous 
variations may be used, this form will prove satisfactory. 
The revolving electrode as well as the stationary elec- 
trodes should be thoroughly insulated from each other 
and foreign bodies. The revolving electrode should be 
insulated from the drive shaft or motor. This is best 
accomplished by using a three-eighths inch shaft and 
bearing for the revolving electrode and making connec- 
tion with the motor shaft by an insulated coupling, such 
as is used in electric light fixtures. These couplings may 
be had for a few cents. Another simple method is to use 
quite a long belt between the motor and a pulley on the 
rotary electrode shaft. The motor used may be an ordi- 
nary small battery motor or a small synchronous motor, 
preferably the latter. Fan motors are desirable for this 
purpose and the power need not be large, since the rotary 
electrode offers very little if any greater resistance to 
the power than a small fan. The stationary electrodes 
need no further comment and may be constructed with 
perforated surfaces to make them wear out evenly, as 
has been described for the series gap. This perforated 
feature may also be embodied in the rotary electrode. 



Construction of a Rotary Plate 163 

The rotary electrode is preferably made out of thick 
sheet aluminum, one fourth of an inch being a suitable 
thickness. The size of the rotary electrode can be from 
four to ten or more inches in diameter, depending on 
the power to be used. An eight inch rotary electrode is 
a convenient size and may be used for stations up to 
24 K. W. or more. To make this electrode, proceed 
as follows: 

CONSTRUCTION OF A ROTARY PLATE 

Find the Center of a square sheet a trifle larger than 
the desired diameter and with it as a radius draw three 
circles. The outside circle will be for the finished dia- 
meter of the electrode, or eight inches in this case. The 
next circle will be a distance nearer the center, depending 
on the size of the electrode. In this case a circle with a 
three inch radius will be used. The inner circle will be 
the size of the shaft used, or three-eighths of an inch in 
this case. Now the circle on the three inch radius is 
divided into eight parts by means of dividers, and these 
points are prick punched. Eight holes, each iy 2 inch 
in diameter, are to be drilled at these points, either before 
or after the plate is turned down to the outside diameter. 
This size of hole leaves sufficient surface to care for 
power up to three-fourths of a kilowatt. The aluminum 
plate should be placed in a lathe and the shaft hole drilled 
out. The outside diameter should also be turned out. 
Aluminum should be worked slowly. Use plenty of ker- 
osene oil. In drilling the holes, care should be taken to 
drill them true. It is advisable to trim the outer diam- 



164 Experimental Wireless Stations 

eter after the plate has been placed on a mandril. The 
simple bearings and mountings need no further comment. 
The stationary electrodes should have a face diameter of 
five-eighths of an inch each, and should be mounted so 
that they are at the center of the electrode holes when 
at that position. The electrode should be mounted so 
that its face runs without wobbling. If a lathe is not 
available, a machinist can be found to do the work for 
you, or a good saw and filing operation will suffice. The 
rotating electrode should be mounted in firm bearings 
to avoid undesirable vibration. 

Note. — The drawing is not to scale. The extra bear- 
ing can be dispensed with and the rotary electrode con- 
nected direct to the motor shaft, using an insulated coup- 
ling as a connector. In the rotary gap the sparking dis- 
tance is best when it is relatively short. If this is not 
maintained as a short space, it will be necessary to use 
less capacity in the transmitting condenser. This last 
is not desirable, since the capacity in small stations is 
seldom any too large. Rotary gaps have a further ad- 
vantage in that they care for heavy discharges without 
heating. Synchronous gaps are those rotated by means 
of a synchronous motor or else attached directly to 
the generator shaft so that sparks occur in accordance 
with the alternations of the supply current. Pure tones 
are produced in this manner. This is not always possible 
when the gap is not driven synchronously. With small 
aerials, the rotary gap allows larger quantities of energy 
to charge the antenna circuit. 

The rotating electrode should be revolved at a high 
rate of speed, that resulting from a direct connection 



Gaps, in General 165 

to a synchronous motor being suitable. The gap need 
only be rotated when in use, and may be stopped, while 
receiving, if desired. 

A makeshift rotary gap can be made by driving evenly 
spaced brass headed tacks or screws into a wood disk 
mounted on a shaft and used as the gap just described. 
Just before the tacks are driven down, a twisted wire 
should be run between them for a continuous connection. 
This gap is not recommended for other than very small 
outfits, and then only as an experiment. The reader can 
doubtless make a more substantial modification along the 
same lines. A good rotary disk can be made by fitting 
silver plated round plugs into a hard rubber or Bakelite 
disk J4 i ncn thick. This disk is then rotated between 
two stationary electrodes. 

GAPS, IN GENERAL 

The surface of the electrodes should always be kept 
clean and bright. Emery cloth is useful for this purpose, 
but after the faces have become worn and pitted, new 
electrodes should be used. Many makeshift gaps are 
easily arranged for emergency or experimental purposes. 
Thus ordinary nails, dry battery zincs, brass pipes, and 
other similar metallic pieces can be mounted and used. 
Common porcelain insulators may be used for insulating 
standards. However, the reader is advised to make a 
substantial efficient gap, whenever possible. Silver makes 
one of the best sparking surfaces. 

It is interesting from the experimental standpoint to 
enclose a spark gap, preferably one of the series type, in 



166 Experimental Wireless Stations 

an air tight container provided with an ordinary bicycle 
valve. Compressed air from a tire pump or carbon dioxide 
from a Presto tube can then be used to increase the num- 
ber of molecules present between the electrodes, and 
under certain conditions surprisingly good results may 
be obtained. 

The reason why a high spark rate is desirable is that 
it can be distinguished and read better than the ordinary 
discharge, and that the individual discharges have an 
additive effect in the receiver, building up a charge which 
results in a good signal. An ordinary discharge does not 
have this building effect upon the receiver, because the 
initial impulse is the actuating force. The subsequent 
impulses resulting from the charge, die out rapidly with- 
out materially affecting the receiving signal. All the com- 
mercial spark stations have adopted a high spark rate in 
one form or another, the rotary gap being quite generally 
used. A rotary quenched gap condJts of two aluminum 
disks, one rotated and the other stationary, both being 
segmented into evenly spaced series of electrodes by 
means of slots milled therein. They are used with a 
short gap and are enclosed in an airtight case. 

ROTARY GAP CIRCUITS 

Fig. 51 shows an ordinary double gap circuit, the motor 
is kept running during the sending only, but is not 
stopped between signals. Fig. 52 shows a rotary gap 
formed by rapidly bringing a , series of insulated elec- 
trodes A between two gaps B and C as shown. This 
is a good series gap circuit. 



The Chaffee Gap 



167 




'Mo for 



Fig. 51.— A Rotary Gap Transmitting Circuit. 
THE CHAFFEE GAP 

Fig. 53 illustrates the gap and circuit of a set which 
is quite successful for small power output. The gap is 
between copper and aluminum electrodes in an atmos- 
phere of hydrogen or alcohol vapor. A direct current 
supply is best and the primary circuit should be tuned 




Fig. 52.— Another Rotary Gap Transmitter. 



168 



Experimental Wireless Stations 



to a wave length 1.7 times the natural wave length of 
the antenna for maximum results. A tone circuit con- 
sisting of an iron core reactance coil in series with a con- 
denser which is shunted by the transmitting key gives 
a musical note to the transmitted impulses. This type 



"Alcohol Cup 



Metals 



Fixed- 



■Choke 





Cooling Vane 
Air Tight- 



- / winnnp — i 



Switch 2- 



Choke 



■Switch I 



mmmskA 




Primary 
Circuit—^ 
■-Tone 
Circuit 

'Resistance 



Antenna 
Circuit 



Switch3^k-^ 

1> 



Telephone 
Trans. 



i^-'Key 



Swihh4 



Fig. 53.— Chaffee Gap. 



of gap can be used on alternating current supply also 
for experimental purposes. With direct current excita- 
tion the gap gives nearly continuous oscillations so that 
by opening tone circuit switches I and 2 and switch 3, 
the telephone transmitter can be switched in the antenna 
circuit by closing switch 4 to afford an experimental 
radio-telephone transmitter. 



Simultaneous Change of Wave 169 

SIMULTANEOUS CHANGE OF WAVE 

LENGTH AND AUDIBLE GROUP 

FREQUENCY 

Fig. 54 shows how a rotary quenched gap can be 
arranged with special circuit so that signals can be sent 
by dots entirely, one dot at a different wave length and 




Fig. 54.— Edelman All Dot, Two Tone, Two Wave Transmitter. 



tone than the other, taking place of the usual dash at a 
saving of time. This method is also valuable in working 
through interferences. U. S. Patent 1214022. 



CHAPTER XII 
Radiation Indicators and Measurements 

Use of Radiation Indicators; Hot Wire Ammeter Construc- 
tion; Wave Meter; Use of Hot Wire Ammeter; Shunt 
Resonator; Cost of Transmitter Complete; Frequency; 
Decrement; Logarithmic Decrement Illustrated; Elec- 
tron Tubes for Measurements; Audion Connected to 
Wave Meter. 

A radiation indicator is a device which indicates when 
the aerial is radiating the maximum amount of energy. 
It is essential to accurate effective wireless work, and is 
used to indicate when the circuits are in resonance. There 
are two types to be described here. The first, the hot 
wire ammeter, is recommended. The shunt resonator is 
perhaps a little easier to construct, but is less reliable 
to use. In addition to the methods described, there is 
an instrument called a wave meter, which, while readily 
constructed, (it is a simple condenser and inductance of 
known dimensions), is unsuited to experimental use un- 
less accurately calibrated. While this can be approxi- 
mated by calculations, this method is tedious and unre- 
liable. However, if a calibrated wave meter can be had 
for comparison, the reader is advised to construct a wave 

170 



Radiation Indicators and Measurements 171 



meter and calibrate it by comparison with the known 
standard, which is very simple. It may be remarked that 
almost any form of variable condenser can be used for 
the capacity and that a few turns of bell wire wound on 
a form about nine inches in diameter will do for the in- 
ductance. A telephone receiver and a detector serve to 
indicate well enough for experimental purposes.* In 
practice this instrument is placed so that the inductance 
is in a parallel plane to the sending helix or oscillation 




Wave Meter 



~Tel. Receiver 



Fig. 55. — Illustrating Use 6f Wavemeter. 



transformer. (See Fig. 55.) It should not be placed too 
near, however, a distance of a few feet being desirable. 
Now, to find the primary wave length with this device, 
the arrangement is as shown at (A) with the aerial and 
ground out of the circuit. The capacity of the wave 
meter is varied until the telephone receiver indicates a 
maximum point. The wave length of the circuit meas- 

* A calibrated resistance (as described on p. 180) may be 
used about the telephone receiver of the wave meter, and 
will materially aid accurate work. A wave meter can be 
used to calibrate a receiving set also. For measurements 
see reference — Bulletin 74, U. S. Bureau of Standards. 



172 Experimental Wireless Stations 

ured is then very nearly the same as that indicated by the 
calibrated wave meter. The operation is essentially a 
comparison of a known wave length with an unknown 
one. The readings should be taken with different turns 
of the helix in the primary circuit Until the wave length 
for the different amounts of inductance is ascertained. 
The wave length for the aerial circuit is obtained in the 
same way, the condenser being disconnected as shown at 
(B). The wave length using different amounts of in- 
ductance in the antenna circuit is then determined. In 
practice the two circuits are connected, so that both the 
aerial and condenser circuits are at the same wave length. 
Thus if the condenser circuit gives- a wave length of 200 
meters with one turn of the helix and the aerial circuit 
gives a wave length of 200 meters by itself when ^y 2 
turns are in circuit, the connections should be made in 
this ratio. If the primary wave length is increased or 
decreased, the secondary or antenna wave length must 
be changed accordingly. The reader is advised to pur- 
chase a wave meter for measurements. Directions for 
use should accompany the instrument. 

In military and some commercial sets a mechanical 
switch makes the correct adjustments in the primary and 
secondary circuit for a calibrated set of wave lengths. 

The hot wire ammeter is used in a somewhat different 
manner. The indicator of the meter is operated by the 
expansion and contraction of a fine wire according to 
the strength of the oscillatory current which passes 
through it, a maximum current causing a maximum de- 
flection of the pointer. This meter is connected in the 
ground conductor directly in circuit with a shunt switch 



Radiation Indicators and Measurements 173 

(SW) which is opened when a reading is to be taken. 
After the adjustments have been made, it is preferably 
short circuited or removed as its resistance impedes the 
oscillations to some extent. The connections are shown 
in Fig. 56. Now, since with a standard experimental out- 
fit, the primary or condenser circuit is to operate at a 
wave length of 200 meters, and the proper relations are 
found by calculation, the hot wire meter will be used to 
bring the secondary or antenna circuit into resonance 



W> 



& 



^ 



i— -- 



=i s 'p0 



Fig. 56.— Hot Wire Meter. 

with the primary circuit, and also to indicate the proper 
adjustment for the spark gap. To operate, connect the 
hot wire meter in the aerial or ground lead, and close the 
primary current. The condenser and inductance of the 
primary circuit are left so that they form a circuit hav- 
ing a wave length of 200 meters according to the calcula- 
tions, and the aerial helix clip is placed at some arbitrary 
point on the helix. The deflection of the meter should 
be noted. Different amounts of the helix* are then con- 

* If an oscillation transformer is used the operation is sim- 
ilar, both primary and secondary, also the coupling between 
them being adjusted. 



174 Experimental Wireless Stations 

nected in the aerial circuit until a maximum deflection is 
obtained, indicating that the circuits are in resonance or 
nearly so. For a wave length of two hundred meters, 
the contact points should always remain at this point and 
the capacity in the condenser circuit should not be 
changed. If the primary condenser is made larger or 
smaller, the whole tuning operation will have to be re- 
peated again. Now leaving the rest of the circuits fixed, 
adjust the length of the spark gap until the meter indi- 
cates a maximum deflection. With this done, the station 
is reasonably sure to be well tuned. If there are no other 
troubles, such as leaks, short circuits, or brush discharges, 
the station is sure to radiate efficiently at the given wave 
length. Increased or decreased wave lengths may be ob- 
tained by changing the amount of the primary inductance, 
re-calculating the primary wave length with the new 
amount of inductance, and repeating the tuning operation 
with the wire meter until the secondary circuit is again 
in resonance. The spark gap need not be changed unless 
the capacity is varied, which is not recommended after 
the proper relations of the circuit are once found. Ex- 
periment will doubtless show that there is one wave 
length or range of wave lengths which will produce a 
greater deflection of the meter than the others at reso- 
nance and if this does not exceed 200 meters it may be 
used, though the adjustment which gives a wave length 
of 200 meters or very nearly 200 meters, with a maxi- 
mum deflection at that point, is to be preferred. When 
a loading coil is used for long wave lengths a similar 
plan is used, the loading coil being regarded as an exten- 
sion to the secondary inductance. When an oscillation 



Construction of a Hot Wire Ammeter 175 

transformer is used, vary the distance between the coils 
to find the best coupling. 

CONSTRUCTION OF A HOT WIRE AMMETER 

A hot wire meter need not be a complicated piece of 
apparatus, since essentially it comprises a mechanical 
movement which will indicate the contraction and expan- 
sion of a fine wire through which the oscillatory cur- 
rent passes. The sensitive part, then, is the bearing and 
arrangement of the movement. The balance wheel of 
an old alarm clock is suitable for this purpose. 

In taking the balance wheel and hair spring out of 
the old clock, leave enough of the framework to hold it 
together. This is all that is wanted from the clock and 
the remainder of the frame should be cut away with 
some heavy tin shears. It is well to clean and oil the 
bearing. 

Mount the balance wheel with its bearings in a wooden 
frame, 8 inches long, 5 inches high and 2^2 inches deep 
as shown in the Figure 57. The frame should be neatly 
and strongly made. The balance wheel should be 
mounted at the center of the bottom piece. 

Put the balance wheel spring into tension by rotating 
the wheel a few turns. 

Obtain a short piece of silk thread (size A or O i? 
suitable), and after fastening it to the balance wheel, 
wind it five times around the axle of the wheel. The 
winding should be arranged so that the pull of the spring 
under tension is checked by holding the thread. That is, 
the thread should be wound in a direction which will 
maintain the tension of the wound up spring. 



176 



Experimental Wireless Stations 



The hot wire itself is made from a small piece of 
No. 36 B&S bare platinum, resistance, or copper wire, 
preferred in the order named. Nichrome or climax re- 
sistance wire serves very well for experimental purposes 
and copper wire will do. Stretch this wire between the 
two binding posts P and Pi, so that it is in a plane above 
the point where the silk thread is wound on the axle. 
This will be clear from the illustrations. Either P or P' 
should be made adjustable so that the tension of the wire 



Pointer. > .'Fastened here 



Spring^ 




Pointer. 

Wheels 
Spring 



EndofSprinq 
fastened here ■ 




HotWire 
^-Thread 

■DiafSpace 
Bearing 



,. -ySottom 



p 



Dial Sea le-' 



Hot Wire- 




: Adjust inq 
Screw 



Fig. 57. — Construction of Hot Wire Meter. 



can be adjusted. This adjustment is necessary to coun- 
teract the natural expansion or contraction of the wire 
under varying weather conditions. 

The pointer can be made either from a thin piece of 
aluminum sheet or a small piece of wood. This pointer 



Construction of a Hot Wire Ammeter 177 

should be made very light and is made 3^2 inches long. 
If this pointer is painted black the readings will be 
facilitated. 

To fasten the pointer, pull the thread so that the 
spring is under tension and fasten one end of the pointer 
to one of the spokes of the balance wheel by means of 
a piece of No. 36 wire or of the silk thread left from 
the other parts. A drop of hot wax or glue will serve to 
make the joint rigid. When fastened, the pointer should 
be in line with the center of the wheel. 

The dial can be made on a piece of stiff paper and 
should be placed close to the back of the pointer so that 
it does not interfere with its movement. The divisions 
on the scale may be any desired number and are used 
only for comparative readings. Commercial instruments 
are generally calibrated direct in amperes or parts of an 
ampere, but for ordinary experimental puposes, com- 
parative readings are all that are necessary. The dial 
should be of a size which will co-operate with the pointer 
and should be placed so that its center point is directly 
above the center of the balance wheel. 

In putting the parts together, place the scale in posi- 
tion first, and tie the silk thread to the No. 36 wire 
at its middle point so that the pointer is moved to the 
o point of the scale. A glass cover and a suitable back 
can then be provided, making a neat instrument. This 
meter will give comparatively large readings for small 
stations, and if large power is used the fine wire should 
be shunted with a coil of No. 26 or 28 copper wire. This 
coil can be wound on a pencil and the amount of wire 
needed must be found by experiment. If this shunt is not 



178 Experimental Wireless Stations 

provided, large coils or transformers will burn the fine 
wire out. A good plan is to start with only one or two 
turns in shunt and if the meter is not operated, add 
more turns until the proper amount is found. Part of 
the current goes through the shunt so that the fine 
wire is not overloaded. 

When an oscillatory current passes from P to Pi the 
fine wire is heated and in expanding it leaves a slack in 
the silk thread which is taken up by the tension of the 
spring. 

This causes the axle to wind up so that the balance 
wheel and pointer move. On account of the small dia- 
meter of the axle and the large leverage of the pointer, 
a very small movement of the thread makes a large move- 
ment of the pointer. When the wire is cooled, it con- 
tracts again and draws the pointer back to zero. It 
will always return to zero when the wire cools again, and 
if it does not on account of weather conditions, the wire 
may be adjusted by either P or Pi (made adjustable) 
so that it does. 

The dimensions given need not necessarily be adhered 
to as long as the general principle is recognized and used. 
By using the balance wheel and hair spring of a watch 
with its delicate bearings, a much smaller and sensitive 
instrument can be made. In this case, a finer wire should 
be used, No. 40 being suitable for an ordinary watch 
spring. The remainder of the instrument should be cor- 
respondingly small, particular care being taken with the 
pointer. 

The success of this instrument depends largely on 
the care taken in its construction, and though very simple, 



Construction of a Shunt Resonator 179 

it should be regarded as a delicate instrument. The cas- 
ing- may be made round or any other shape and can be 
of metal if the parts are well insulated from each other 
and the metal. 

The hot wire ammeter is very desirable because it 
indicates the maximum radiation better than any other 
simple apparatus. While the wave meter does this to a 
certain extent, its use is limited to the actual measure- 
ment of wave lengths and is not very useful in determin- 
ing the maximum radiation. 

CONSTRUCTION OF A SHUNT RESONATOR 

This arrangement acts as a radiation indicator and 
serves the same purpose as the hot wire meter except 
that it is less delicate and sensitive in its indications. It 
has the advantage of not interfering with the oscillations 
and can be left in circuit continually. The arrangement 
is shown in Fig. 58. The coil is constructed like a helix, 
about a dozen turns of No. 8 wire wound on a form three 
inches in diameter and spaced one-fourth inch apart, with 
a movable contact, being suitable. The lamp used is a 
small four or six volt carbon filament bulb, and may be 
had at any supply house. Whenever the transmitter is 
in operation the lamp lights up. 

The coil is connected as shown in shunt around six or 
more feet of the ground wire, the proper amount to be 
determined by experiment. Only a part of the high fre- 
quency current is passed through the coil by this arrange- 
ment so that the resistance of the ground wire is not 'in- 
creased. It is really decreased to some extent. The 



180 



Experimental Wireless Stations 



effect is probably due to the resonant relation of the coil 
and the section of the ground wire. 

To find the maximum radiation at a desired wave 
length, place the slider of the indicator coil so that all 
the turns are in circuit and adjust the antenna circuit 
until the lamp lights up the brightest. Now decrease the 
number of turns, on the indicator coil, thus decreasing 
the brilliancy of the lamp, and adjust the transmitting 
circuits again. Continue this process until the lamp lights 
up brilliantly with the least possible number of turns of 
the indicator coil connected in circuit. The transmitting 



■ |7k ? rg=Hj 










to Transmitting Instrumtnts-^ 


/ 

Shunt Coil-' 




A 










J& 



Fig. 58.— Shunt Resonator to Indicate Radiation. 



station will then have a maximum radiation for a given 
wave length. A similar arrangement can doubtless be 
used by substituting a hot wire meter for the lamp, in 
which case, the radiation can be read directly. This is 
likely to be hard on the meter, however. 

We have now considered the transmitter and its sev- 
eral details in some degree of thoroughness, paying par- 
ticular attention to the resonant relations of the circuits 



Construction of a Shunt Resonator 181 

and the design of standardized instruments. It is well 
to again remind, that all of the circuits should be well 
connected, contact points clean and of even surface, spark 
gaps clean and properly adjusted, and everything ar- 
ranged in as workmanlike a manner as possible. 

A word as to cost. The cost of a station depends 
largely on the individual. Some experimenters are able 
to construct and operate efficient sets which cost only a 
few dollars, while other less experienced or less fortu- 
nate workers may spend many times as much without 
better or even as good results. A good 250 watt station 
to operate at a wave length of 200 meters can be con- 
structed at an average cost of about $30 for the trans- 
mitter, though the actual figures may be considerable 
more or less in each case, according to the circumstances 
involved. This figure does not consider the item of 
labor, transportation charges and many other variable 
factors, and indicates little more than the cost of the 
materials used. While larger stations (larger power) 
do not necessarily follow in the same ratio^ the expense 
may be taken roughly as an additional $20 for every 150 
additional watts. This amount is not to be taken as fixed 
or even accurate, as there are so many variable factors 
concerned. As an example, the hot wire meter described 
in this chapter will be made by many readers at a total 
expense of less than 25c, while others will doubtless 
spend up to a few dollars in its construction. In gen- 
eral, then, it is well to make the several parts as sub- 
stantial and neat as possible without an excessive expen- 
diture. After all, the "Works are more important than 
the looks," though good appearance is also desirable. 



182 Experimental Wireless Stations 

Receiving stations can be made at a cost of perhaps 75c 
or up to as much as you wish; Designs for receiving ap- 
paratus will be found in later chapters. 

The need of thorough insulation throughout is per- 
haps most important of all and all insulation should be 
quite thick in order to avoid the dielectric effect. In wire- 
less transmission, a great deal of energy may pass through 
an insulator to a foreign body on account of the capa- 
city which is formed. Thick insulation cuts down the 
capacity and consequently avoids this effect. With reso- 
nant, well adjusted circuits and a well insulated aerial, 
very good results may be expected. In fact with these 
precautions observed better results may often be had 
from a small outfit than from a much larger outfit in 
which the several points are not well carried out. 

ACCURATE MEASUREMENTS— FREQUENCY 

Although many who read this volume are not directly 
concerned with accurate measurements in radio work it 
seems wells to mention that one can determine a wealth of 
facts by using the wavemeter, the hot wire ammeter, or 
both. Knowing the wave length for instance one can 
immediately determine the frequency of the oscillations 
in the aerial. Thus frequency equals 1,000 million di- 
vided by wave-length in feet. A wave length of 10,000 
feet (nearly two miles) for example means that the fre- 
quency is only 100,000 and it is evident that lower wave- 
lengths mean, under like conditions, higher frequencies. 
Other quantities such for instance as the decrement can 
also be obtained with accuracy and facility. For com- 



Decrement 



183 



plete information on radio measurements see the Bureau 
of Standards Bulletin No. 74. 

DECREMENT 

Logarithmic decrement means the logarithm to the base 
2.17828 of two successive maxima of the wave ampll- 



j-Resonance 
Mar. Current 




ft Max.Current 




C. CoC* 

Capacity Used 



Hot Wire Milliammeter 
Wavemeter 



Circuit being 
measured 



Fig. 59. — Measurement of Decrement 

tudes in a wave train taken in the same direction. Thus, 
Figure 60. 

d=io g £.• 



l¥ 








wTn~ATTA7 


rn~A* 






\ni\l 


Y 

• 







Fig. 60. — A Wave Train Illustrating Logarithmic Decrement. 
* Standard American Practice. 



184 Experimental Wireless Stations 

Expressed in terms of resistance, inductance and ca- 
pacity of the circuit concerned d = fl"Ry 5 . 

L 

In the case illustrated there will be 23 oscillations in 
the wave train before the amplitude dies down to one 
per cent of its starting value. 

MEASUREMENT OF DECREMENT 

Decrement is best measured by a special decremeter but 
may be determined as follows: Figure 59 shows a resonance 
curve plotted by reading the current in the wave meter with 
a hot wire ammeter (or thermo-junction galvanometer 
method). When the wave meter is at the same frequency 
adjustment as the transmitter the resonance peak occurs. 
The decrements of the transmitting and of the wave meter 
circuits, d lf d 2 , determines the sharpness of this peak portion 
of the curve. The capacity of the wave meter condenser is 
noted at the point of resonance and called C Q . The capacity 
is then both increased and decreased therefrom to get the 
two valves Q t C 2 at which the wave meter responds with a 
current induced into it equal to one-half of the maximum 
current value. If the decrement d t of the wave meter itself 
is known, the decrement of the circuit being measured is, 
closely, 

2 -/ VCo-/ "" d 

or roughly, when d„ is very small 



d 2 



/ Co-CA 



The Kolster decremeter is a specially constructed wave 
meter, having logarithmic condenser plates, which reads this 
value directly. Its condenser is varied until I max. is ob- 



Electron Tubes for Measurements 



185 



tained, then varied to the value C. The gears of an auxiliary 
scale give d x and d, and are meshed to the condenser handle 
so that when a pointer is set at zero and the condenser is 
rotated to give the value C 2 , the decrement d is indicated 
directly. 



ELECTRON TUBES FOR MEASUREMENTS 

Electron tube generators afford controllable constant 
intensity and frequency sources very valuable for meas- 
urement purposes. 5 to 500 watts output at 2 to 
50,000,000 cycles per second can be had. Full informa- 
tion for such, technical measurements may be found in 
Bulletin 74 of the Bureau of Standards. 

SIMPLE MEASUREMENTS WITH AUDION 

GENERATOR CONNECTED TO WAVE 

METER 

Fig. 61 shows a very convenient form of wave meter 
having its own tube oscillator. A detector bulb may be 



Circuit 
xilnder Test 



.20-40 Volts, 




Galvanometer 



jrpn X 


, U I ft" V 

■4}, JPrr 



"W Substitute for T 
Fig. 61. — Seif-Oscillating Wavemeter. 



used. The circuit L. C gives the wave length and a scale 
on the variable condenser handle can be calibrated di- 
rectly in meters. This device can be used as a buzzer 



186 Experimental Wireless Stations 

test, as the local oscillator in a heterodyne receiving cir- 
cuit, or as the secondary of a complete autodyne (self 
heterdyne) receiving set. Two such wave meters can 
be readily calibrated against each other if one is already 
calibrated as beats there between when both are oper- 
ated cease when the wave lengths are exactly equal. 
Also, as in the case shown, any unknown circuit of in- 
ductive capacity can be calibrated directly by closely 
coupling the wave meter inductance L to it. As the 
handle of C is moved a sharp transfer of energy be- 
tween the two circuits occurs at resonance and this 
"burr-up-click" is heard in the telephones T so that it 
is easy to ascertain the wave length directly with suf- 
ficient accuracy for most purposes. The improvised 
thermo couple V consisting of two twisted iron and 
copper wires can be used with an inexpensive galva- 
nometer of the torsion type in series with the con- 
denser W to give quantitative indications of resonance. 
The high frequency oscillations heat the thermo-couple 
(or a crystal detector substituted therefore) and gen- 
erate a direct current which operates the galvanometer. 
Close coupling produces a remarkable effect and, rela- 
tively, loose coupling is necessary for accurate reso- 
nance indications. The effect of coupling changes at 
Z can be studied in this manner. 



CHAPTER XIII 
Advanced Systems 

Continuous Waves; Wireless Telephone; Quenched Spark; 
High Frequency Alternators; Demonstration of Arc 
Radiotelephone; Poulsen Arc; Construction of Quenched 
Gap; Lepel Gap; Advantage of Quenched Gaps; Wire- 
less Piano; Goldschmidt Alternator; Alexanderson Al- 
ternator; Magnetic Modulator; Static Transformer Fre- 
quency Multiplier; Onde Unique System; Vacuum Tube 
Methods; Duplex High Speed Operation; Wave Chang- 
ing Systems. 

The more advanced methods of wireless communica- 
tion utilize continuous waves, produced either by an arc, 
quenched spark, or direct high frequency generator. In- 
asmuch as these methods are quite likely to be developed 
into the ultimate perfected wireless system, some con- 
sideration of the theory together with experimental opera- 
tion is worthy of attention. 

A simple system that may be used for telegraphy or 
telephony is shown in Fig. 62. This arrangement will 
only operate on direct current of 220 volts or more. The 
power supply should be capable of furnishing a uniform 
current of 10 amperes. The arc light may be an ordinary 
arc, but the lower electrode is preferably made of brass 

187 



188 



Experimental Wireless Stations 



or copper and water cooled. This water cooled electrode 
may easily be made from a plumber's T connection, using 
a brass plug for the electrode end. Rubber tubing can 
be used to connect the T to a water supply. The arrows 
indicate the flow. The aerial, ground and oscillation 
transformer may be the same as for the spark system 
already described. The condenser should be variable, as 
the exact amount of capacity must be found by experi- 
ment. A hot wire meter in the aerial can be used to 
indicate the correct adjustment of the circuits. The im- 
pedance coil is made by forming an iron core ij4 in. 



n£ 



;Water Res/stance 

, /Impedance Coil 



A V 

Key. — 



Choke Co/7-^ 



Carbon-^ 
P 



'220-500V.D.C 



rrrrrr""" 

r'/ev ' — i 
WllllliQ: 



lev 

B0ffer^\\\\rQ- 



I .Uii.i ip 



\ 



Arc- 



m 



Two Tarn Coif-, 
'Condenser 



C 

'Copper 



fm^i<- 



°=j=2_J " "Transmitter 
^Key 



" *~<hoke Coil-Single Winding 
■Not Used 



t T 



P 



Water Cooled 



7 



Fig. 62. — Demonstration Set for Arc Wireless Telephone. 



square and 5x8 in. outside dimensions, as for a trans- 
former, winding about four pounds of No. 12 D. C. C. 
wire on the long legs. The purpose of the impedance 
coil is to prevent the oscillations from surging back into 



Advanced Systems 189 

the generator. The choke coil is made similar to the 
impedance coil, except that only two pounds of wire 
are used and wound on one leg. If desired, a secondary 
can be wound on the other leg. (See chapter on trans- 
formers.) A resistance for the arc should also be pro- 
vided. This may be made by placing two electrodes an 
adjustable distance apart in a solution of salt and water. 
A transmitter or a key can be shunted around the choke 
coil, acco/ding to the use to be made of the set, or the 
key or transmitter may be used to vary other parts of 
either the primary or aerial circuit. A current through 
the secondary winding of the choke coil may also be used 
when it is modified by a transmitter. Caution: 220 to 
500 volts are dangerous, so be careful. 

It is understood, of course, that the transmitter in 
Fig. 62 is used instead cf a key when the circuit is used 
as a wireless telephone, or vice versa. That is, a key 
may be substituted for a transmitter to form an experi- 
mental arc telegraph. If the key or transmitter is used 
in the aerial, a duplicate in the main arc circuit is not 
needed. For telephone experiments the transmitter is best 
shunted around the choke coil as shown in the lower 
insert of Fig. 62. Only the choke coil and transmitter 
(Tr.) are shown in this insert, as the circuit is the same 
in other respects. In this case only one winding is 
used. If the two windings are used as shown, the trans- 
mitter is connected to the secondary winding through a 
battery. In this method the variations caused by the 
transmitter are superposed on the line current by induc- 
tion and in turn cause variations in the arc circuit. In 
the shunt method the transmitter carries part of the cur- 



190 Experimental Wireless Stations 

rent directly, while in the inductive method it is only 
indirectly connected to the main circuit. Ordinary trans- 
mitters can be used. It is advisable to use two or three 
connected in parallel and grouped as a single unit. Larger 
currents can be cared for in this manner. The author 
has passed from i to 4 amperes through an ordinary 
transmitter with good results. The transmitter was 
heated by this treatment, however, and in some later 
trials, it was burned out. Indeed, the art was formerly 
hindered for want of a satisfactory transmitter, but this 
difficulty has largely been obviated by use of amplifying 
and vacuum tube methods. 

It should be noted that the oscillatory circuit is formed 
by the condenser, oscillation transformer and arc. The 
circuit through the resistance, impedance coil, arc and 
choke coil is used to excite the arc. 

In operation, the condenser is alternately charged and 
discharged at a very high rate, because the voltage be- 
tween the arc terminals decreases with an increase of the 
current. The condenser takes current from the arc, caus- 
ing an increase of the voltage between the terminals, and 
as a result more current flows into the condenser. Even 
after the condenser is charged to the same potential as 
that between the arc electrodes, the current in the con- 
denser continues because of the inductance in series with 
it. The potential difference at the condenser thus be- 
comes more than at the arc terminals, so that the con- 
denser now begins to discharge through the arc. This 
immediately causes the voltage of the arc to drop, so that 
the discharge continues. Finally the condenser potential 
falls below that of the arc electrodes and the process 



Advanced Systems 191 

reverses again. The condenser continues to charge and 
discharge in this manner and the resulting oscillatory 
current is utilized in the transmission. The arc is varied 
by the transmitter or key and in the former case, causes 
the arc to reproduce the sounds spoken into the trans- 
mitter. The resulting oscillations are similarly varied so 
that the receiver gets a more or less exact reproduction 
of the transmitted sound waves which are sent as electro- 
magnetic waves. 

The frequency produced in an arc system is very high, 
being from 100,000 to 1,000,000 per second, and as it is 
not interrupted, cannot be heard by the receiver except 
when modified by a telephone transmitter or key with 
tone circuit such as shown for the Chaffee gap. Very 
close tuning is necessary to get results from this circuit, 
and the experimenter who is specially licensed therefor 
is quite safe in using any reasonable wave length with 
this arrangement. It is less efficient at low wave lengths. 
For best results the inductance, P, should be relatively 
large and the condenser, C, small. 

A singing arc is made by connecting variable capacities 
in the shunt circuit of the arc. The pitch varies accord- 
ing to the capacity in this case, the highest pitch being 
obtained by the use of a very little capacity. If a tele- 
phone transmitter is also used the arrangement forms a 
talking arc. This is the same as the wireless telephone 
just described but without helix, aerial and ground. It 
is also possible to omit the condenser for this purpose. 
Words spoken into the transmitter are reproduced by the 
variations in the arc. The sound will be louder as the 
length of the arc is increased. (Do not look at the arc 



192 



Experimental Wireless Stations 



too much, as it is very bad for the eyes.) It is best to 
enclose the arc in an insulated metal box. 

An arc system allows very sharp tuning to be car- 
ried out, and as a result it does not interfere with other 
stations, as much as ordinary spark sets do. The per- 
sistent train of oscillations produced by this method is a 
decided advance in the wireless art. The received signal 
is an accumulated impulse resulting from a series of the 
oscillations. The arrangement described will only oper- 
ate over short distances, however, as large power and 
specially designed arcs and apparatus are necessary for 
long distance work. 

POULSEN ARC 



The arrangement of a Poulsen arc is shown in Figure 
63. The carbon electrode is slowly rotated with respect 
to a cooled copper electrode in the field of a strong elec- 



.'Res/'stance 

, Aw» 




— < TflJU C\ 



• Choke Coil 

Fig. 63, 



-A Small Poulsen Arc. 



The Lepel Arc System 



193 



tromagnet in a hydrocarbon vapor or gas as shown. In 
large stations several hundred kilowatts can be converted 
into radiant energy by the powerful water cooled arcs 
employed. The key merely alters the wave length of 
the emitted impulses by simultaneously closing several 
short-circuiting contacts every time it is depressed. The 
receiver hears two waves, the sending one containing 
intelligence and the. compensating one which results in 
between signal elements when the key is raised. Often 
both can be plainly heard at the receiving station. Some 
of the largest stations now use this type of transmitter. 

THE LEPEL ARC SYSTEM 



This arrangement is a combination of the arc and 
quenched spark systems now little used in the United 
States. It operates on either direct or alternating cur- 
rent of 500 or 1,000 volts. This voltage may be ob- 
tained from an ordinary alternating current supply by 

V 






"1 

Fig. 64. — Lepel Transmitter. 



194 



Experimental Wireless Stations 



means of a step up transformer. A five hundred watt 
step up transformer with a ratio of I to 5 will serve 
nicely on no volts A. C. for experimental purposes. 
The arrangement is simple and is shown in Fig. 64. The 
condenser used can be made of paraffined paper on ac- 



Can with water- 




Fig. 65. — Detail of Lepel Gap. 



count of the low voltage used, but glass is recommended. 
The remainder of the apparatus with the exception of 
the arc or gap itself is familiar and needs no further 
comment. A suitable construction for the gap for experi- 
mental purposes is illustrated in Figure 65. Ordinary tin 
cans can be utilized, but the electrode faces should be of 
copper turned smooth and having a groove as shown. 



Wireless Piano 



195 



This groove serves to prevent the arc from reaching the 
outside of the gap. These copper disks should be from 
3 to 5 inches in diameter, and can be arranged, after the 
cans are filled nearly full of water. The two electrodes 
are separated by a circular disk of paper, not more than 
.01 in. thick. A good bond paper will do. The disk 
should have a small hole at its center to afford a starting 
point for the arc. 

WIRELESS PIANO 

The circuit for direct current supply is shown in Figure 
66. If the tone circuit is switched in, a musical note of 
any desired tone can be emitted. Indeed, it is possible 



ToneC/rcv/f-.'flj^$$ 



= =: Switch- *[ XT7 




azzzz * Amrqefer' 

Lepe/Arc- 



Fig. 66. — A Wireless Piano. 



to arrange a keyboard as a "wireless piano" by placing 
contacts on the inductance I as shown. Without a tone 
circuit the emitted energy cannot be heard except at 



106 Experimental Wireless Stations 

stations equipped to receive substantially undamped 
waves. 

In operation the arc starts at the center and gradu- 
ally burns the paper away. As this burning occurs in 
in an atmosphere lacking in oxygen, the paper does not 
burn all up until after a number of hours. It is essential 
to the arc, that the distance between the electrodes should 
be uniform and not over .01 inch, so that the arc occurs 
in an atmosphere lacking in oxygen. The products of 
combustion of the paper also aid the arc's efficiency. 

The paper disk can be renewed after it is used up. 
This gap gives practically continuous oscillations and the 
circuits can be tuned by using a hot wire meter. This 
form of gap can be utilized for telephone purposes in 
much the same manner as described for the arc. Great 
care should be taken in handling the circuits as a shock 
from the line or secondary might easily prove fatal. 
Two or more of these gaps may be connected in series, 
this method being suitable for higher voltages. 

TELEFUNKEN QUENCHED GAP 

This is really a number of Lepel gaps connected in 
series. This arrangement can be substituted for the or- 
dinary gap of a spark system. The disks are turned as 
shown from 3-16 or % i ncn sheet brass to an outside 
diameter of 6]/ 2 or 7 inches and grooved iori^ inches 
in, so that the groove is about 3-8 of an inch wide at the 
face. Each plate is grooved on one side in this manner. 
See Fig. 67. 

The mica rings used may be had at supply houses and 



Telefunken Quenched Gap 



197 



should not extend further in than 1-8 inch beyond the 
outside diameter of the groove, so that the inside cir- 
cumference of the mica comes within J4 i ncn of the in- 

,,'D/sc 



T 



'Mica 



j—-^-- 



Vm^> 



Groove-' 




'Groove A/rSpace 

Fig. 67.— Quenched Gap. 



side circumference of the groove. The groove is to pre- 
vent the spark from jumping to the mica as the latter 



198 Experimental Wireless Stations 

becomes a conductor when heated by a high frequency 
discharge. The mica rings should not be more than .01 
inch thick. The disks are assembled in pairs so that 
the grooved faces are next to each other, and washers 
are placed between the pairs so that the pairs are sep- 
arated by a distance equal to the thickness of one of the 
plates. Thus if *4 mcn plates are used, the washers used 
should be % inch thick. The assembled gap may be 
suitably mounted by using insulated supports, a sufficient 
number of pairs being used so that the combined length 
of the gaps is somewhat less than the length of a single 
gap, ordinarily used. When large power is used with 
this gap, it is well to have a small fan blow upon it to 
dissipate the heat which is generated. 

THEORY AND ADVANTAGES OF THE 
QUENCHED SPARK 

The gaps described are not difficult to construct and 
operate and are recommended to the readers. The dis- 
charge is practically noiseless, almost 60 per cent more 
efficient than a common gap, and produces nearly un- 
damped waves. A high pitch note, which increases the 
effective transmission range, can also be had. 

The operation of the quenched gap depends upon 
the fact that the spark quenches itself out after it has 
made a few oscillations, allowing the secondary oscilla- 
tions to continue freely. This was illustrated in Figure 31. 
The primary circuit is thus opened so that it does not 
interfere with the secondary or aerial oscillations. As a 
result the unwelcome beats common to open spark sys- 



Advantages of the Quenched Spark 199 

terns are avoided. Returning to the parallel case of a 
gong, the quenched spark may be compared to a padded 
hammer, which after striking the gong (comparable to 
the antenna circuit in this case), a forceful blow, allows 
it to continue by itself with a clear, powerful vibration. 
The short spark gap when well cooled prevents the pri- 
mary from oscillating by itself after the secondary circuit 
has been excited. That is, the spark is active only long 
enough to allow the secondary oscillations to reach a 
maximum, and the secondary oscillations are a maximum 
after the primary oscillations are reduced to a minimum. 
The number of primary oscillations necessary for this 
ideal operation is governed by the degree of coupling 
between the primary and secondary. It is desirable to 
use a close degree of coupling with the quenched spark 
for this reason. The energy ordinarily lost as heat in 
an ordinary spark gap is thus conserved and the wear on 
the primary apparatus is reduced. One of the chief 
causes of heat in the condensers and wear of the gap with 
an ordinary open gap is the useless continuance of the 
energy after the useful oscillations have been generated. 
The quenched gap, then, prevents undesirable oscillations 
from being set up in the primary by the reaction of the 
secondary, and makes the resulting radiations have a sin- 
gle wave length, for receiving purposes. 

In constructing the quenched gap, it is essential that 
the electrodes be pressed with some force against each 
other. In the Lepel form of gap described the weight of 
the upper electrode suffices, but in the form of Arco gap 
described, a clamp should be provided. A quenched gap 
in connection with a resonant outfit as described in pre- 



200 Experimental Wireless Stations 

vious chapters is an ideal set for the experimenter. These 
arrangements are also known as shock excited systems, 
and are rapidly coming- into increased favor. Commercial 
quenched gaps use silver surfaced electrodes. 

Note. If mica is not obtainable in the necessary size, 
rubber sheet of uniform thickness .01 inch may be used, 
though the mica is to be preferred. Stove repair compa- 
nies carry mica in stock as do commutator concerns. The 
latter use a mica mixture which is much cheaper than 
mica and which is suitable. Smaller dimensions may be 
used for the electrodes for small stations, and for very 
small stations one or two sets of plates will suffice. By 
using soft rubber sheet instead of mica the length of the 
gaps can be varied by varying the pressure on the plates. 
Sheets of soft rubber can be had at dental supply houses. 
The quenched gap is of course used like a regular spark 
gap in an experimental set. Quenched gaps are made in 
both stationary and rotary forms, the latter having ad- 
vantages similar to those of an ordinary rotary gap as 
well as those of the quenched gap. 

HIGH FREQUENCY GENERATORS 

While beyond the facilities of the average experimenter 
some description of certain other systems is of interest. 

The Goldschmidt high frequency generator has been 
tried for long distance work. Its operation depends upon 
the fact that an armature mechanically rotated in a ro- 
tating magnetic field gives an initial frequency — say 
10,000 — which can be further stepped up by carrying the 
current back through the field to produce a more rapidly 



High Frequency Generators 



201 



rotating magnetic field; this new frequency current is 
again led back to still further increase the frequency, 
and so on until the desired frequency — say 40,000 — is 
attained. The circuits must of course be nicely balanced 
electrically in order to obtain the necessary resonance, 
condensers being used for this purpose. To avoid eddy 
current losses, the armature is constructed of iron foil 




fChoke Coil 
'~fl 000000 1 



Fig. 68. — Goldschmidt Alternator. 



only .002 inch thick, each sheet being insulated from the 
next one. Substantially undamped waves are emitted by 
the use of this machine and since the frequency is above 
audibility, the method of beats is employed to get the 
intelligence at the receiving station. 

The arrangement is diagrammed in Figure 68. Here 
the initial 15,000 cycles is obtained initially by use of 
high speed and large number of poles. This causes an 
oppositely rotating field thereby set up to give 30,000 



202 



Experimental Wireless Stations 



cycles which is in turn returned back to the rotor to 
give 45,000 cycles and again transferred to the antenna 
circuit which is tuned therefor at 60,000 cycles. The in- 
ductance and capacity in each circuit is chosen so as to 
select out the desired frequency. 

ALEXANDERSON ALTERNATOR 

The Alexanderson alternator as used successfully at 
one of the large U. S. Naval stations is diagrammed in 
Figure 69. A high speed (20,000 R.P.M.) rotor of the 
inductor type carrying a large number of teeth is in- 
serted between the yoke on which are wound the field 
coil F and armature coils A, A. A special magnetic 
amplifier M controls the large output by direct absorp- 



IIOV.D.C. 

rlHH 



Key may be used 
here if Mis not 
in circuit 



W^YoAe 



■Alternator 




Magnetic Amplifier 
used for control - 



Transmitter may 
be used instead 
of key for radio' 
telephone* 



Fig. 69.— Alexanderson Alternator. 



High Frequency Generators 



203 



tion. When the key is depressed the core of M has 
its magnetization altered so that a maximum current 
is permitted to flow in the antenna circuit, and vice 
versa. 

Still another method for producing sustained oscilla- 
tions has been devised by Galletti. Direct current is 
used as the primary source and a plurality of oscillatory 
circuits are automatically excited in succession, a com- 
mon condenser being coupled to these circuits. 

An experimental alternator has also been constructed 
in which the primary frequency is multiplied by means 
of a polarized transformer. 



■/rans formers 





'Iron Cces 



Nx Current 



Fig. 70. — Static Transformer Frequency Multiplier. 



The method of doubling the frequency with stationary 
transformers is illustrated in Figure 70. Each trans- 
former 1 and 2 has two primary windings connected 
as shown, one to a battery B and the other to the al- 
ternator F. The secondaries is, 2s are tuned to double 
the primary frequency. As indicated by B of the ap- 
pended magnetization curve each transformer has its 
core brought to the saturation point by the battery B. 



204 Experimental Wireless Stations 

The primary connections are such that the flux increases 
in transformer I while it decreases in transformer 2, so 
that in one half cycle a small increase in flux in 2 with 
a large decrease in i occurs. The opposite takes place 
in the next half cycle so that each half cycle is effective 
in causing a whole cycle to occur in the secondary wind- 
ings. 

It is possible to triple the initial frequency by adjust- 
ing the two transformers' magnetization so that one 
causes a peaked wave containing a strong third harmonic 
while the other sets up at i8o° therefrom a flat topped 
wave containing the same harmonic so that the harmonic 
alone can be tuned for in the secondary circuit by dif- 
ference. If an alternator gives 10,000 cycles this ar- 
rangement permits it to be changed up to 30,000 cycles 
which is equivalent to 10,000 meters wave length. 

The French "Onde Unique" system is illustrated in 
Figure 71. An intermediate heavy turn circuit A is in- 
serted between the usual transmitter B and antenna C. 
D shows the equivalent circuit. A single wave length 
impulse is emitted by the antenna with this arrangement. 



== • sHb c J* ^ == 

JNJOi 1 1 * L. 




Fig. 71.— Onde Unique Circuit. 



Duplex High-speed Operation 205 

VACUUM TUBE METHODS 



Vacuum tube transmitters have grown to an import- 
ance requiring special consideration and are discussed 
in the chapter covering this subject. 

DUPLEX HIGH-SPEED OPERATION 

Large radio stations are operated duplex, that is, 
messages can be received and sent at the same time by 
using two antenna systems, one for sending and one for 
receiving. The transmitter is then usually remotely con- 
trolled by electromagnet switches. All the large Navy 
Transatlantic Stations are controlled directly from 



Insutaton 




Fig. 72. — Lowenstein Wave Changing Switch. 

Washington, D. C. This is done by means of magnet- 
ically operated relay switches. 



206 Experimental Wireless Stations 

High speed operation is accomplished by using auto- 
matic senders and recorders. The former are usually 
of the punched tape type and the latter are photographic 
or phonographic or telegraphonic. Radiotelephony can 
also be operated multiplex. 

WAVE CHANGING 

Nearly all military and naval transmitters are provided 
with special switching devices to permit rapid change of wave 
lengths. There are many ways in which this is done, some 
also being arranged to alter the resistance or reactance of 
the primary exciting circuit at the same time the wave 
length is changed; so as to maintain the most efficient cir- 
cuit relations at all adjustments. A well-known example is 
shown in Fig. 72. Both the primary and secondary circuits 
are simultaneously altered. 



CHAPTER XIV 
Vacuum Valves and Circuits 

Vacuum Tubes; Amplifiers; Detectors; Oscillators; Modu- 
lators; Tube Radiotelephones; Experiments Showing 
Fundamental Action; Two and Three Electrode Tubes; 
Curves of Operation; How the Circuits Work; Opera- 
tion of Grid; Audion Circuits; Lieben Reisz Amplifier; 
Pliotron; Cascade Amplifier; Outside Grid Tube; Dyna- 
tron; Chart of Vacuum Tube Circuits for all Purposes; 
Ultra-audion Receiver; Damped and Undamped Wave 
Circuits; Audion Generator; Armstrong Circuit; Con- 
struction of Long Wave Length Oscillating Receiver; 
Adjustment of Oscillating Circuit; Short Wave Length 
Repeating Amplifying Receiver; Cascade Circuits; Ad- 
vantages and Disadvantages of Audion; Combined Crys- 
tal Detector and Audion; Sensitizing Circuits; Special 
Vacuum Tube Circuits; Self-tuned Oscillation Genera- 
tor; Self-Modulated Transmitter; New Tube Circuits. 

The vacuum tubes which have come into universal use 
for detecting, amplifying, generating, modulating, and 
special work offer a good transition point from trans- 
mitting to receiving apparatus because used for both. 

The beginner should now first read Chapter XVI on 
"Receiving Stations." 

There are several types of these bulbs, but aside from 

207 



20& 



Experimental Wireless Stations 



details of construction and modified mode of use, the 
general operating principles are the same. 

EXPERIMENTS SHOWING FUNDAMENTAL 
ACTION 

In the curve of Figure 73, a large change of the plate 
voltage (Battery B) causes but a small change of the 
plate current flowing through ammeter A in the region 
(1) and also (3) but near (2) a small change of B 
gives relatively a large change in A. 

When the third electrode or grid is interposed be- 

1 






8-Vctried 

Electron pf^||hi(||| 
FJow-^ 




,^=® 



10 



70 



40 
Vol+s-B Bat+ery 

Fig. 73. — Two Electrode Vacuum Tube. Current Flow with 

Constant Filament Brightness and Varied Plate Voltage. 



tween the filament and plate and its potential is varied 
with other conditions constant as shown in figure 74 a 
similar curve is obtained so that in the region (4) a 
small change of the grid potential causes a large change 
in the current flowing through A. 



Detector Action Shown By Curves 



209 



Current flows from the plate to the filament only when 
the grid is made less negative than the point which stops 

^--Constant 

llllllK 




VJ 
< 










Z> 










U 










-C 










«i 


















Q. 










fc 

»5 


Negative 




— ^Positive 





•10 



-5 Volts 



+5Volts 



► 10 



Grid Potential 

Fig. 74. — Three Electrode Tube. Flow of Plate Current at 
Various Grid Potentials. 



the electron flow. Current flows readily, of course, if the 
grid is neutral or even positive. 

DETECTOR ACTION SHOWN BY CURVES 

In Figure 75 it will be seen how the incoming energy 
causes a telephone current corresponding to the audible 
group frequency to be set up. The grid potential is 
negative, the plate current positive, and the telephone 
current derived from the latter is smoothed out be- 
cause of the inductance lag in the telephone receiver's 
windings. 



210 



Experimental Wireless Stations 



A combined rectifier and amplifier results when the 
grid condenser is used because the incoming oscillations 
are rectified and stored in this condenser C 2 so that the 




incoming Oscillations 




'Time 



^%l/irC^\vi/\r 




91 ate Current 




Fig. 75. — Detector Action Shown by Armstrong Curves. 

charge and discharge thereof causes the telephone re- 
ceivers to respond at audio frequency. 

PRINCIPLE OF OPERATION 

It should be remembered that there are two distinct 
actions of this class of valves, the one holding for bulbs 
containing appreciable gas so that ionization can occur 
by collision and the other taking place in bulbs so highly 
evacuated as to be almost free from gas so that a purely 



Principle of Operation 211 

electronic action occurs. The first class of bulbs may be 
recognized by the blue glow which occurs just beyond 
the sensitive and operating adjustment as in the audion. 
The Lieben-Reisz, Audio-tron and similar tubes are also 
of the first class. The second class embraces bulbs such 
as the pliotron in which a pure electron discharge occurs 
from the heated cathode or filament. The second class 
does not rely upon residual gas as a conducting medium. 

The hot filament in these devices emits electrons. In 
elementary static electricity it will be remembered that 
like charges repel and unlike attract; negative repels 
negative for instance. The electron may be considered 
as the smallest possible particle of electricity, the atom 
of electricity so to speak, and furthermore it is always 
negative. Hence if an electron comes near a negative 
charge or a piece of metal charged negatively by a bat- 
tery the electron will be repelled, or on the other hand 
the same piece of metal if charged positively will at- 
tract the electron to it. 

Now in a highly evacuated bulb containing filament, 
grid, and plate, the resistance between the filament and 
grid or plate when the filament is cold is very high, and 
a pressure of 100 volts for example can send no current 
across such a path. As soon as the filament is heated, 
however, electrons are emitted from the hot cathode and 
fill the surrounding space. As soon as the space is filled, 
however, additional electrons which are emitted by the 
filament cathode are repelled by the electrons already 
in the space and are absorbed again by the cathode. If 
now the grid, which is between the plate and the fila- 
ment is negatively charged by a battery still more elec- 



212 



Experimental Wireless Stations 



trons will be repelled and sent back to the filament, but 
on the other hand if this grid is positively charged the 
electrons will be attracted to it and a larger current will 
flow from the filament. This is the case for the pliotron. 
When, however, there is gas present, as in the audion, 
the electrons in passing from the filament to the plate 
ionize the gas, that is split it up into elementary parts 
carrying electric charges so that the gas becomes a con- 
ductor. Now some of the charges of the ionized gas are 
positive and these partly neutralize the electrons which 
have been projected into the space by the filament. Also 
if a positive charge is applied to the grid the electrons 
from the filament will be attracted and pass more 
rapidly. In so doing they produce more ions in the gas 
and the action continues — more electrons pass the grid 




I 




HiHH 



£> 



Bz 30V 

Fig. 76. — Audion Receiver. 



and more ionization takes place. Now every time ioniza- 
tion occurs or increases the electrons in the space are 
reduced so that a much larger current can flow from the 
filament. Only a small amount of gas need be present 
for this purpose. In fact if too much gas is present 



Principle of Operation 213 

there will be too much ionization and too large a current 
will flow giving a blue glow and spoiling the relaying 
effect. 

On such a basis we can understand what happens in 
the tube. Fig. 76 shows the ordinary audion circuit. 
Both detection as in a crystal rectifier and amplification 
of the received energy by trigger action occur. In use 
the filament is brought to incandescence and tuning ad- 
justments are made until the desired signals are brought 
in. The incoming signals are embodied in oscillations 
and these are rectified between the filament and grid. 
One-half cycle passes, the other cannot because the hot 
filament — cold grid is uni-directional. If the grid con- 
denser C 2 is omitted and the circuit at this point closed, 
a somewhat different action occurs. In the Fleming 
valve this is all, but in the audion under consideration 
amplification now occurs. The battery B 2 causes current 
to pass from the plate to the filament but by the action 
already explained the negatively charged grid decreases 
it. When this current decreases the change registers 
on the head phones and a loud response results which 
is much stronger than would result from the rectification 
alone. The potential on the grid caused by the incoming 
oscillations controls the larger current passing from the 
plate to the filament and through the phones to give the 
signal. A small increase of the potential on the grid 
means in practice a large change in the current passing 
between the grid and filament, and this in turn causes a 
corresponding change in the current passing through the 
phones by way of the plate to filament circuit. 

The audion generally works best just below the point 



214 



Experimental Wireless Stations 



which causes a blue glow to appear. The filament should 
not be lighted when the set is not in use because this re- 
sults in a waste of current from the high voltage battery 
and deteriorates the filament. When the filament is 
lighted and the device is ready to use, the high voltage 
battery causes a continual flow of current through the 
bulb: the incoming oscillations merely cause this current 
to vary. 

FLEMING VALVE 

The Fleming valve, one of the first of these, consists 
simply of a miniature electric light bulb with a filament 



,- Filament Valve 
—Valve 




Fig. 77.— Fleming Valve. 



and a metal plate near it as shown in Fig. 77. In use, 
current may pass from the filament to the plate but not 
reversely so that the device acts as a rectifier. It is not 
very sensitive and relatively few are in use now, The 
kenotron is a similar device which is evacuated so that 
less gas is left in the bulb. The kenotron is very highly 



AUDION 



215 



evacuated and built for larger current but is not used 
for wireless purposes at present. In these devices the 
resistance varies with the applied voltage differently than 
by Ohm's law. 

AUDION 

The audion (Fig. 76) is like the previously described 
device except that a grid, which is simply a piece of bent 
wire or metal screen or plate with holes, is placed be- 
tween the filament and the metal plate or wing. The 




*#" fy 7Z 



30 Volt Battery; 



Fig. 78. — Lieben-Reisz Circuit. 



audion usually has a double filament, only one filament of 
which is heated at a time, the other being saved for use 
when the first burns out. This filament is connected to 
a 6 volt storage battery through a small rheostat. Sepa- 
rated from the filament by about % inch is the plate 
and between the two at the middle and insulated from 
both is the grid. The plate is about y£ inch square and 
of sheet nickel in the size used as a detector. The whole 



216 



Experimental Wireless Stations 



is sealed in a glass bulb and evacuated so that only a 
little gas is left. Various other forms have been made 
with two plates and grids, in larger sizes, with cylin- 
drical plates, etc., but the principle of operation is the 
same in all types. The device called the pliotron is 




FlG. 79.— Lieben-Reisz Tube. 



similar in all respects except that the bulb is very highly 
evacuated. Experimental bulbs have also been made in 
which mercury vapor is introduced into the bulb after 
it has been evacuated. 



LIEBEN-REISZ AMPLIFIER 

The Reisz gas tube as described in U. S. patent 
1,142,625 is shown in Fig. 78. The circuit in which it 
is used is given in Fig. 79, T 1 and T 2 are iron core step 



Pliotron-Cascade Amplifier 



217 



up transformers. The device is analogous to the audion 
which is better known and will be understood from dis- 
cussions of the latter device. 

PLIOTRON-CASCADE AMPLIFIER 



This device has two plates, a grid of fine wire wrapped 
around a support F (Fig. 80) and a filament held in 

Pliotron, 




Fig. 80.— Pliotron Tube. 

this support. It is very highly evacuated so that much 
higher voltages must be used with it than in the case 
of the audion. It can be built in larger sizes than the 




*=?-, I i_JL. l_2 

f/Q 75 




tg 75 
Fig. 81.— Cascade Radio Frequency Amplifier. 



218 Experimental Wireless Stations 

audion for use as an undamped wave generator or relay 
and is more constant, so that whereas audions vary 
widely in characteristics, these more highly evacuated 
bulbs are nearly identical and many of them may be con- 
nected in parallel. Two such devices connected in cas- 
cade for receiving radio signals with an amplification 
as high as 1,000 times are shown in Fig. 81. L 1 and L 2 
are the primary and secondary of an air core trans- 
former. The first bulb detects and amplifies the in- 
coming oscillations and the second bulb again amplifies 
the previously amplified oscillations. The battery B' 
must afford several hundred volts and the battery B" 
is required to charge the grid. A similar circuit may be 
used with ordinary audion bulbs except that batteries B" 
are not required. 

OUTSIDE "GRID" TUBE 

While less desirable a so-called "grid" can be wound 
on the outside of the tubes and connected as in Figure 82. 



i li 



Tube-'' 



* 



Plate A I I 

— f ■ 

. I . Vuts 



a ^Outside Grid 



Fig. 82. — A Vacuum Tube with an Outside Grid. 



Vacuum Tube Circuits 



219 



DYNATRON 

A form of tube called the Dy natron is shown in Figure 
83. It has a rugged third electrode D with a special 
circuit such that at some adjustments the tube delivers 
back sufficient energy (derived from battery B) to off- 




Fig. 83.— Dynatron Detector. 

set or more than offset the resistance its circuits have. 
This is called "negative resistance" and can be attained 
with an ordinary audion bulb if desired. 

VACUUM TUBE CIRCUITS 



A number of useful vacuum tube circuits, including 
the most generally used ones, are shown in Figure 84. 

I. shows the ordinary two element rectifier which con- 
ducts from plate to filament, but not reversely. Small 
arrows indicate electron flow from filament, while large 
arrow shows current flow from battery. 



220 



Q 



Experimental Wireless Stations 

^Incoming Groups Amp/ified^^ 




FigJ 
Rectifier 



Impressed 
Frequency 




Radio 
Frequency 



oq 



Audio Frequency 
Fig.YE 
Amplifier 



Fig.H 
Repeater 



r Q 



ESQ 



Grid 
Battery."-' -1^1 

Fig. Ill 
Rectifier with Grid 
Control 



W ,'1,000,000 Ohms 

&p*m,,'Gr/'d 
A Condenser 

IOC 





Core 



Fig.IZ 
Grid Series Condenser 
^ with Resistance Leak 



Fig.inil 
Edslman Combined Amplifier 



^KljftJU f> 



Filament 



\& 



Ur_ii# 



flft ---Feed Back 
***• (Loose Coupling) 



Fig.K 

Generator 



S=l 



Regenerator Amplifier 



-Open- 




Fig.X 
Grid Operated Receiver 



?IG. 84.— An Interesting Collection of Vacuum Tube Circuits. 



Vacuum Tube Diagrams 221 

II. shows a third element or grid added. This takes 
some of the electrons so that the current flow through 
T is reduced as long as the grid remains negative and 
stops altogether if the latter is sufficiently negative. But 
when the grid is neutral or positive, current flows freely 
from the plate to the filament from the battery B. The 
impressed positive half cycle increases this current flow 
while the negative half cycle decreases it, making the 
current through T rise and fall therewith, the amount of 
distortion, if any, depending upon the adjustments. As 
energy is taken from B, increased power is obtainable 
through T at the impressed frequency. 

III. shows a grid control battery added to adjust the 
grid potential. Starting with a negatively charged grid 
the effect of a negative half cycle impressed is small but 
a positive half cycle causes a large increase in the plate 
current through T. If the grid is made positive to start 
with by reversing the grid battery the opposite result 
is obtained. 

IV. shows the grid series condenser with high resist- 
ance leak. Radio frequency energy is rectified and a 
negative charge accumulates on the grid side of the 
small series condenser. This further reduces the plate 
current flowing through T until the shunt leak permits 
the charge to escape when the oscillations cease to arrive 
from the antenna circuit. The grid returns to normal 
potential then, and as this is repeated for each audible 
group of radio frequency oscillations the receivers T 
get a corresponding (and amplified) audio frequency 
excitation. 

V. Figure 84 shows the feed back or repeating circuit 



222 Experimental "Wireless Stations 

added so that enormous amplification up to the capacity 
of the tube results. If the coupling of the feed back 
coils is close the tube becomes a generator as shown in 
IX. 

VI. shows cascaded radio and audio- frequency ampli- 
fiers. Seven stages can be used without "howling" trouble 
by proper grounding and shielding of the separate cir- 
cuits and give enough amplification to permit the use of 
a relay in place of the telephones T. Amplification up to 
2,000,000 times input audibility is possible though usually 
less than 1,000,000 times suffices. 

VII. shows resistance coupled amplifier tubes which 
while less intense for the same number of bulbs in cas- 
cade requires less auxiliary apparatus and is free from 
"howl." The resistances R are high resistance units and 
a single battery suffices for all tubes up to 10. 

VIII. shows a combined amplifier devised by the au- 
thor which feeds back from the last to the first bulb and 
has the iron, core magnetization adjusted for maximum 
results by exciter D. 

IX. shows a simple single coil generating circuit. 

X. shows an open circuit grid potential operated re- 
ceiver claimed by Bucher. 

EFFECT OF MAGNET ON AUDION 

If a magnet, permanent or electromagnet, is brought 
near an audion in operation various effects may be pro- 
duced. This may be accomplished by passing current 
through a coil of wire wound about the vacuum tube 
itself. Sometimes this merely causes the blue glow to 



The Ultra- Audion Receiver 



223 



appear. In other cases the bulb starts to send pulsations 
through the phones at a rate which gives musical tones 
which may be made to run all the way up and down the 
scale by proper motion of the magnet. If, however, the 
magnet is brought in the proper plane the thermionic 
stream can be concentrated so that in very many cases 
the bulb will work better than ever and give an increased 
amplification. This may be quickly found by trial. 

THE ULTRA-AUDION RECEIVER 

De Forest's ultra-audion is a form of heterodyne cir- 
cuit combined in one instrument. It is an ordinary 




= G 



MihT 

Fig. 85. — Qltra-Audion Receiver. 



audion detector with a receiving circuit (Fig. 85) in 
which the inductance L is large (secondary of loose 
coupler wound with many turns of No. 30 to 36 wire) 
while the condenser C is only about .0002 microfarad 
in capacity. The condenser VC is also made small. The 
.electron flow in the audion used in this circuit is auto- 
matically unbalanced because of this system of induc- 
tance and capacity so that continuous oscillations are set 



224 



Experimental Wireless Stations 



up. These oscillations are strengthened by the variable 
condenser C". Any audion bulb may be connected up 
in this manner to receive undamped wave signals. When 
the capacities are adjusted so that the audion sets up 
oscillations slightly differing in frequency from those 
received, beats result which are heard in the head re- 
ceivers. 

Often an ordinary audion in a common receiving set 
will oscillate in such manner if only the filament is 
burned slightly brighter than usual. One may ascertain 




; Microphone 



Fig. 86. — Armstrong Regenerative Circuit. 



that the bulb is oscillating by touching any portion of the 
metallic circuit between L and C whereupon a sound 
will be heard in the telephone receivers if the bulb is 
oscillating. For receiving from spark stations the bulb 
is often best when in the non-oscillating condition as 
when oscillating in the above manner the musical tone 
of the sending spark becomes ragged so that a louder 
but indistinct sound results. This is a sensitive arrange- 
ment for detection as it affords a combined detector and 
amplifier as well as a local oscillator. 



Audion as Undamped Wave Generator 225 

AUDION AS UNDAMPED WAVE GENERATOR 

A suitable circuit for obtaining undamped waves from 
an audion bulb is shown in Fig. 86. A microphone may 
be employed as shown so that for demonstration pur- 
poses the arrangement shown may serve as a wireless 
telephone transmitter for some little distance. The fila- 
ment of a bulb intended for a detector will, however, 
rapidly waste away, so it is best to obtain a bulb con- 
structed for this purpose. Any frequency can be obtained 
over a wide range by adjustments of the condenser 
capacity. 

ARMSTRONG CIRCUIT 



The Armstrong circuit combines the principle of the 
singing microphone with the audion so that a part of the 
amplified current reacts on the current between the grid 
and filament and thus causes a still further amplification. 



Auction^ 




Fig. 87. — Long Wave Oscillating Circuit Receiver. 



226 



Experimental Wireless Stations 



This is best accomplished by means of a coupling coil 
built like a loose coupler. If this coil is made with an 
air core (no iron) the radio frequency oscillations will 
be amplified. Similarly by the use of an iron core in- 
duction coil the audio frequency current through the 
telephone will be amplified. It is possible to amplify 
either or both at the same time. In Fig. 87 the complete 
circuit for a long wave set using the oscillating and 
amplifying audion is given. Either spark or undamped 
wave sets can be heard with this arrangement. A less 
complicated circuit which will serve about as well is 
shown in Fig. 88. Compare with the ultra-audion, Fig. 

85. 

CONSTRUCTION— LONG WAVE UNDAMPED 
WAVE RECEPTOR— RANGE 14,000 METERS 

Few of the readers have the facilities to construct 
the bulbs, but if one has a bulb the amplifying circuit may 
be readily made at small cost. When properly adjusted 




Fig. 88. — Simple Armstrong Circuit. 



Adjustment 227 

a single bulb amplifier of this type is as good or better 
than the usual two step amplifier employing two bulbs. 

The values of the condenser capacities and maximum 
battery voltages are given in the diagram of Fig. 87. The 
inductances are made by winding a single layer of silk 
covered wire on paper tubes and for the various coils 
suitable dimensions follow. 

L 1 ; core 6" diameter by 25" long wound with No. 24 
S. C. C. wire, with taps taken at ten, five, and then every 
inch of length. 

Loose coupler L 2 , L 3 . Primary L 2 ; 12" long by 6" 
diameter with No. 24 S. C. C. Secondary L 3 ; 12" long 
by $y 2 " diameter wound with No. 32 S. C. C. 

L 4 and L 5 are each 5" in diameter and 30" long, and 
wound full of No. 32 S. C. C. Taps are taken every 
inch at the last 5 inches. 

Loose coupler L 7 , L 6 . L 7 is 8" long by 5" diameter. 
L 6 is jy 2 " long by 4^" diameter. Both cores are wound 
full of No. 30 S. C. C. wire. 

The condensers should be of the rotary plate type and 
C 2 which is used at very small values should have a 
streak of graphite rubbed between its binding posts to 
serve as a high resistance shunt which dissipates high 
voltage accumulations on the condenser from static dis- 
turbances. 

ADJUSTMENT 

Short circuit L 5 and place C 3 at its maximum capa- 
city. Have L 2 , L 3 all in and vary L 4 and the other con- 
densers, also L 1 until the signals are brought in best. 



228 Experimental Wireless Stations 

Now place L 5 in and adjust the number of turns used as 
well as C 3 until the loudest signal strength is obtained. 
Mark the adjustments for future reference and make 
any other necessary changes -by means of L 1 , L 2 , L 3 , C 3 , 
and C 1 . When the bulb is replaced with a new one, the 
adjustments may have to be repeated as new values will 
be required. If siren effects bother, ground one terminal 
of battery B. 

Fig. 8? will now be readily understood. The loose 
coupler L 2 , L 3 is made with variable coupling, L 2 is 5" 
in diameter* by 4^2" long. L 3 is 4^2" in diameter by 
5" long. Both cores are wound full of No. 28 S. C. C. 
B 2 should be adjustable up to 40 volts. The range will 
depend on the loose coupler used between the aerial and 
detecting circuit and is more suited to wave lengths under 
6,000 meters. 

SHORT WAVE REPEATING AMPLIFIER RE- 
CEIVER 

With slight change the usual regenerative circuits will 
work nicely on 200 metres. See Fig. 89. 

The antenna is 75 feet long and 50 feet high, two wires 
inverted "L" type, or if a multi-turn coil is substituted for 
indoor receiving, thirty turns of No. 20 D. C. C. wire are 
wound on a frame five feet square, no ground being used in 
the last case. 

The condensers have the values shown in the diagram. A 
tubular audion operated" on 6 volts is suitable. 

As to the tuner; wind twenty-five turns No. 22 D. C. C. 
wire in a single layer on a tube three inches in diameter and 
one and one-half inches long, for the primary. Wind a sim- 
ilar tube for the secondary but two and three-fourths inches 
in diameter and with fifty turns of No. 26 D. C. C wire. 



Cascade Circuits 



229 



Now wind a third coil on another tube about three inches 
in diameter and such that it will just slide over the end of 
the primary tube; this coil to have ten turns of No. 22 D. 
S. C. wire. Mount the three coils similar to a loose coupler 
so that the secondary and the third coil are adjustable with 
respect to the fixed primary coil. 



O.P.D.l Switch^ 



1500 Ohms-. 



3b—, 




Fig. 89.— "Tickler" Oscillating Circuit. 

Connect per diagram, and operate as usual. When the 
third coil is out ordinary signals can be heard. Then 
when the double pole switch is thrown to connect in 
the third coil, the repeating amplification starts. Also short 
wave beat reception becomes possible by suitable adjustment 
of the tuning condensers. 

CASCADE CIRCUITS 



Audions may also be used in cascade to amplify either 
the audio or radio frequency currents. Pliotrons can 
also be used in a similar manner. There is a limit to 
the number of steps that can be used, however, as the 
amplified current soon causes distortion, so in practice 
not more than three bulbs in cascade have been found 
to be practicable. In the cascade circuits it will be noted 



230 



Experimental Wireless Stations 



that the first step is the familiar circuit while the ampli- 
fied current of this step (at audio frequency in the audion 
arrangement) operates the grid filament circuit of the 
next step through an iron core inductive coupling; then 
this is repeated in the next step in the same manner. 
The final current may be large enough to operate a loud 



V 



Transformer 



= G 




Fig. 90. — Cascade Audio Frequency Amplifier. 

speaking telephone or even a relay or milliameter. Often 
signals with any of the audion circuits have been so 
loud that they could be directly recorded on a wax 
cylinder phonograph by simply holding the telephone re- 
ceiver against the recording diaphram. 



CASCADE CIRCUIT CONSTRUCTION 

Fig. 90 shows how to connect two ordinary audion 
bulbs in cascade to amplify the audio frequency. Com- 
pare with Fig. 81 and note that these two figures could 
be combined to still further increase the magnification. 



Disadvantages of Audion 



231 



The transformer consists of a core i" in diameter and 10" 
long made up of a bundle of soft iron wires wound with 
tape. The primary winding consists of one pound of 
No. 36 S. S. C. wire. Over this the secondary of one 
and one-half pounds No. 36 S. C. C. wire is wound. 
Amplification up to about 100 may be expected. 

DISADVANTAGES OF AUDION— COMPARI- 
SON WITH CRYSTAL DETECTOR 

The audion detector as now sold is bulky, fragile, 
and requires frequent care and renewal of batteries, bulb, 
etc. Many bulbs are not constant and some give annoy- 
ing siren effects. In many cases there really is no need 
to employ any such device for a crystal detector will do 
as well or better. A crystal detector such as galena will 
even detect signals from arc and undamped wave sets 
under favorable conditions. The author has heard such 
signals when using such a detector in a receiving circuit 
containing a variometer coupler which caused the neces- 
sary reaction in the circuits. The tone, however, was not 
musical. 




Fig. 91. — Crystal Detector Combined with Audion Circuit. 



232 



Experimental Wireless Stations 



The audion as an amplifier is superior, as the usual 
received signals are amplified to advantage. Indeed the 
audion may be combined with a good crystal detector to 
advantage, the one rectifying, the other amplifying the 
rectified current. 

AUDION WITH CRYSTAL DETECTOR 

The connections for using an audion with a crystal 
detector such as galena are shown in Fig. 91 and afford 




Fig. 92. — Combined Audio and Radio Frequency Feedback. 



an amplification of about 10 times the signal strength 
obtained with the detector alone. 



Combined Frequency Feed Back 



233 



COMBINED AUDIO AND RADIO FREQUENCY 
FEED BACK 

Figure 92 shows how both the radio and audio fre- 
quencies can be fed back to repeat again. The condensers 

2 are of large size, for example, .2 m.f. each while the 
condensers, 1, are of the small air type. Iron core coils 

3 form so called "tone circuits*' with condensers 2, i.e., 
these circuits have an electrical period corresponding to 
a low frequency or audible tone. 

In the arrangement of Fig. 93 the grid potential is 




Fig. 93. — Receiver with Adjustable Grid Potential. 

adjusted by shifting the potentiometer contact t and the 
plate voltage by potentiometer contact p so that the 
first adjustment limits the current which can flow while 



234 



Experimental Wireless Stations 



the latter setting aims to secure the best response for this 
condition. In short, the tube is operated near the flat 
portion of its curve so that strong strays do not have 
nearly so much relative effect on the receiver m as do the 
signals received. 

RECEIVER WITH SENSITIZER 

Fig. 94 shows an auxiliary sensitizing circuit which 
has been used by the U. S. Navy. It consists of a wave- 
meter coupled to the grid circuit and adjusted for maxi- 
mum response in the telephones T. 




Fig. 94. — Sensitizing Circuit in Receiver. 



Fig. 95 shows a tube combination circuit which has 
been used and known as "Meissner's receiver" though 
quite similar to others. 

Fig. 96 shows another modified circuit which has been 
used by the Marconi Company. 



Audiox Laboratory Circuits 



235 




B C 

Fig. 95. — Meissner's Receiver 



imiiiiiiiiH 

B 




Fig. 96. — Marconi Receiving Circuit. 

AUDION LABORATORY CIRCUITS 

Fig. 97 shows suitable circuits proposed by White 
which can be used for laboratory or therapeutic purposes. 

s'High Voltage Output 
■4H+ 





Fig. 97.— Audion Connections for Either High Voltage or 
Heavy Current for Laboratory Experiments. 



236 



Experimental Wireless Stations 



A GENERATOR WHICH TUNES ITSELF 

In Fig. 98 a very simple oscillating circuit is shown 
which may be used as a radio-phone transmitter or an 
autodyne (self heterodyne) receiver. The frequency is 
here determined by the constants of the separate oscil- 

_ _w 



1 
1 

J Oscillatory 
}£? Circuit 

^' ^Equivalent 
of 
~-^Y —An tenna 

I 
I 
I 
I 



S Grid 
Circuit 




Plate Circuit 



-3KH 



Transmitter 



Fig. 98.— A Self -Tuned Oscillating Generator. 

lating circuit (antenna-ground) coupled to the plate and 
the grid circuits so that the circuit is very well suited to 
the home experimenter's needs. 

SELF-MODULATED AUDION TRANSMITTER 

Fig. 99 shows how an audion generator can be used 
as a transmitter to give signals which may be received 
on an ordinary crystal detector set. 



CONVERTED FREQUENCY AMPLIFIER 

Recently a nine-step short wave length amplifier has 
been developed on the beat principle to convert the 



Converted Frequency Amplifier 



237 



short waves at high frequency to longer ones at less 
frequency. The latter are then amplified as usual with 
much greater efficiency than formerly. A diagram of 
such a circuit as constructed by an amateur is given 
in "The Wireless Age" for January, 1920, but is too 
complicated for use except by the advanced reader. 

(Audio Frequency, 

<-• Audio Frequency 



w 




Fig. 99. — A Circuit for Self-Audio Frequency Modulated Groups 
of Sustained Radio Frequency. 



CHAPTER XV 
Tube Radiotelephones 

Modulation Systems; Portable Radiotelephone; Transconti- 
nental Wireless Telephone; Connection of Tubes; U. S. 
Army Set; U. S. Navy Set; A Wireless Telephone Oper- 
ated from Your Lamp Socket; Power Tube Radiotele- 
phone; A Small Amateur Radiophone; Cost of a Tele- 
phone Set. 

COMBINED MODULATION 

Starting with a telephone transmitter, this may be used 
to grid modulate one vacuum tube which in turn is cas- 
caded to several others, the last of which repeats into 
an Alexanderson-Nixdorf magnetic amplifier, which 
latter controls directly the output of a large high fre- 
quency alternator. As much as ioo kilowatts can be 
modulated in this manner from an ordinary telephone 
transmitter. 

Figs, ioo, 101, 102, 103 show suitable circuits for 
radiophones with range up to about ten miles when a 
vacuum tube receiver is used. Larger ranges can be ob- 

238 



Combined Modulation 



239 



tained by increasing the power handling ability of the 
generating tubes used. The "grid modulation" shown is 
very effective and requires no large current capacity 
microphone transmitter, as is obvious, because the output 
is potentially controlled. 



V 




~~260 turns #20 wire on core 3"Dia 
^^4— Ordinary Transmitter 



Figs. 100, 101, 102, 103.— Radiophone Circuits. 



Tubes are now built in sizes up to I K. W. each. 
The largest ones are made from "pyrex" heat resist- 
ing glass and have tungsten metal parts so that the 
plate can be run red hot. 



240 



Experimental Wireless Stations 



COMBINED PORTABLE RADIOTELEPHONE 
AND TELEGRAPH SET 

Fig. 104 shows a multi-turn coil combined radio tele- 
phone and telegraph transmitter and receiver devised by 
the author for short range work requiring no antenna. 



A Variation 




Station 2 

Oscillating Bulb 
Fig. 104.— Portable Tube Radiophone and Telegraph Set. 

This is an excellent set for demonstration as well as 
other obvious purposes. 

TRANSCONTINENTAL WIRELESS TELE- 
PHONE 



In 191 5 wireless telephone, one way communication 
was established from Arlington, Va., to Paris, France; 
Honolulu, Hawaii; Colon, Panama, and a few other 
places. On the basis of the author's own independent 
experiments, previous to the above mentioned tests, it 
is probable that the circuits employed were of the type 



Transcontinental Wireless Telephone 241 

i 

shown in Fig. 105. There are various modifications for 
the same result.* 

In this figure the current from a telephone line is 
amplified through an audion bulb in the manner already 
set forth and this amplified current is used to actuate the 
grid-filament circuit of a large number of highly evacu- 
ated bulbs connected in parallel and arranged to gener- 
ate undamped waves after the manner already set forth. 



,-Pliotrons 



Microphone 




Fig. 105. — High Power Wireless Telephone. 



An ordinary telephone transmitter may thus be used to 
vary the strength of the high frequency oscillations set 
up in several hundred bulbs and where one bulb is shown 
in the diagram it will be understood that any suitable 
number of bulbs may be substituted in a similar manner 
to secure, higher power. Continuous radiation occurs in 
the aerial-ground circuit and this is modified in exact 

* First complete publication was given as above in the 1916 
edition of. this book. 



242 



Experimental Wireless Stations 



r-<Sh 




sl — mmmm — t 



t 6 




Transcontinental Wireless Telephone 243 

accordance with the voice which causes the original 
variations of the electrical current which are amplified 
and made to control the larger current at radio-fre- 
quency. This will be readily understood by bearing in 
mind the previous discussions of the parts here com- 
bined. Any receiving station with a sensitive detector 




Carrier Wave Detector Intermediate Freq. Detector 

MULTIPLEX RADIOPHONE RECEIVER 



■238 Meters Oscillator 



Power tubes giving modulated power 
,-to Antenna at 238 Meters 






T 



I 



MULTIPLEX TRANSMITTER 



« 
<=>j 

=" 



~*-2£G00^ 
Oscillator 



W>rH(r— f 







Modulated tube giving modulated 
power to toned circuit. 



---Speech Amplifier 



Fig. 107.— Multiplex Radiotelephone System. 



244 



Experimental Wireless Stations 



such as an audion with amplifying circuit can receive 
from such a wireless telephone station and the voice 
reproduction will be even better than over land lines. 

Transcontinental radio-telephony is an assured success 
in the immediate future for general commercial use. 

ARMY AND NAVY SETS 



Fig. 1 06 shows the aeroplane radiophone used by the 
U. S. Army. The vacuum voltage regulator keeps the 
generator voltage used to supply the transmitting bulbs 
constant at various speeds. See paper by Craft and Col- 
pitts, A.I.E.E., Feb. 21, 1919, for further details. 

Fig. 107 shows the principle of multiplex radio-tele- 
phony. The emitted waves are doubly modified, first 
at radio and then at voice wave frequency so that several 



LF.Choke Coil 



,-H.E Choke Coil 




Modulator 



Fig. 108. — U. S. Army Radiotelephone Modulator. 



voices can be carried by the same transmitter at one time. 
At the receiver there is a tuned circuit to select the radio 
frequency modified received wave which in turn is de- 
livered to the proper detector. This principle is used 
also in multiplex line telephony. 



Army and Navy Sets 



245 




»8 









i 

i 

i 
i 
•t 







246 



Experimental Wireless Stations 



Fig. 1 08 shows the modulator used in army radio- 
phone sets. 

Fig. 109 shows the U. S. Navy radiophone. A small 
oscillator is grid modulated and repeated into several 
power tube amplifiers which supply the antenna circuit 
as shown. Circuits of this type can be arranged to give 
transmission over a range of 100 to 5,000 miles, depend- 
ing upon the power used. 

A WIRELESS TELEPHONE OPERATED ON 
YOUR LAMP SOCKET 

Fig. no shows how three connections, A, B, C, will 
give a serviceable short range radio transmitter and re- 
ceiver of fixed wave length requiring no further adjust- 
ments after initial installation. For receiving contact D 



\Choke 



Aerial 




IIOV.DC 
Plug to lamp soccer 

Pes. 




Fig. 110.— Wireless Telephone Operated from Lamp Socket. 



Power Tube Radio-Phone 



247 



is moved to end E instead of one-fifth from this end as 
for transmitting. A similar set has been developed for 
alternating current by using a rectifier. 

POWER TUBE RADIO-PHONE 

Fig. in shows an oscillating tube generator devised 
by the author to handle large power inputs. The ad- 




Fig. 111.— Edelman Air-Cooled Oscillating Tube. 



vantages are obvious. The usual manner of voice modu- 
lating the continuous waves is employed as indicated. 



248 



Experimental Wireless Stations 



AN AMATEUR'S RADIO-PHONE 



The experimental set herein described uses from fifty to 
ninety volts of the large size tubular flashlight batteries or 
No. 6 dry cells. 

The continuous wave generator in this outfit described by 
F. R. Pray (W. A., Mar., 1919), consists of two small, three 
element vacuum tubes such as tubular bulbs or electron re- 
lays with the members connected in parallel. Additional 
bulbs may be added to increase the range, which should be 
from two to six miles per bulb, depending on the tuning of 
the circuit and the efficiency of the antenna and ground. 

Figure 113 gives the front and side view of the assembled 
outfit. The front panel should be made of some good insu- 
lating material such as Bakelite. The base and back may be 
of hard wood treated with asphaltum varnish or a mixture 
of lamp-black and shellac as they are touched by no current 
carrying connections. On each side of the panel, about 9 
inches up from the base, two wooden strips 7 inches .long 
should be placed between the back and front, to strengthen 




Fig. 112.— A Small Radiotelephone Set. 



An Amateur's Radio-Phone 



249 



the construction. These are not shown in the side view as 
they would cover up the wooden, inch square strips which 
support the two secondaries. These hinge from the pri- 
mary with these strips as axes. See diagram, Fig. 112. 

Each of the two secondaries, S.,^ and S 2 , is composed of 
five turns of edgewise wound copper strip spiral 7^ inches 
in diameter, 1/2 inch wide and 1/16 inch thick. Each turn 




Fig. 113.— Arrangement of Small Radiotelephone Set. 



is held ¥% inch apart from the adjoining turn by strips of 
Bakelite, 1 inch square and 2 inches long, except at the 
bottom. The coil is fastened to the axis upon which the 
secondary pivots by a piece of Bakelite shaped as in Figure 
3-A. The primary, P, is composed of copper, spiral wound 
edgewise as the secondaries and is 5 inches in diameter, 5/16 
inch wide and 1/16 inch thick. Each adjoining turn is held 
Y% inch apart by Bakelite strips, Y\ inch square and 5 inches 
long, except at the bottom, where the primary is supported 
by a piece of Bakelite as in Figure 3-B. This piece is to 
be fastened to a strip of wood, held between the front and 
back panels by wood-screws as in the side view of Figure 2. 



250 Experimental Wireless Stations 

The copper strip for the "oscillation transformer" may be 
purchased from supply houses. 

The transformer is considerably heavier than necessary 
for the current derived from the high voltage battery as 
suggested here, for the experimenter sooner or later may 
find himself in a position to use power bulbs and a commer- 
cial form of high voltage supply. 

In most radiophone circuits a radiation indicator (such as 
a hot-wire ammeter) is essential, for successful operation 
depends mainly on careful tuning. The hot wire meter 
shown may be purchased for a few dollars or be made as 
described elsewhere in this book. Battery B 3 is comprised 
by six dry cells, ignitor type, or a storage battery. Coil I 
is a telephone transformer obtainable for a few cents from 
used apparatus dealers. Battery B 1 is a six-volt, ten-ampere 
hour storage battery. The rheostat switch in the lower left- 
hand corner is iy 2 inches in diameter and has twelve points 
of variation. 

Any audion or equivalent bulbs costing around $5.00 each 
may be used. Condenser VC should have about 36 plates 
with total capacity of .005 infd and should be immersed in 
cylinder oil. 

The range of the set is 175 to 350 meters with usual 200 
meter type of aerial. 



CHAPTER XVI 
The Receiving Station 

Operation of Receiver; Telephone Receivers; Purpose of De- 
tector; Energy of Signal Received; Types of Detectors; 
Principles of Operation. 

Having considered the transmitter and its details, as 
well as vacuum tubes, the receiving station details will 
now receive attention. The aerial and ground have al- 
ready been discussed and since they are the same in 
most cases for both transmitter and receiver, they need 
no further attention. 

We have seen that the transmitter emits waves of 
definite lengths and having definite characteristics, ac- 
cording to the adjustment of the transmitter and that 
these waves are spread out in all directions at the speed 
of light. Now at the receiver, all that is necessary is 
some apparatus which will detect the waves which strike 
the receiving aerial and translate them into an intelligible 
signal. 

For this reason, the apparatus in its simplest form con- 
sists merely of a detector and a telephone receiver con- 
nected in the antenna circuit. This is shown in Fig. 114. 

251 



252 



Experimental Wireless Stations 



It will be understood that other sensitive recorders 
such as an Einthoven galvanometer can be used instead 
of the telephone receiver. The detector, however, is 
essential, because even the most sensitive telephone re- 
ceiver or galvanometer cannot record signals without it. 




Fig. 114. — Simple Crystal Detector Receiver. 



In early experiments, a relay was used for the record- 
ing instrument. In its most sensitive form, however, a 
relay will only operate with about .001 of a volt at its 
terminals. Further, its action is slow, so that it has been 
discontinued for signalling purposes. Its use is limited 
to the field of telemechanics, the art of controlling motors, 
boats, etc., by wireless through a local relay. Its co- 
operating detector, the coherer, has also become obsolete 
except for the purpose mentioned. ^ 

The telephone receiver is the instrument in universal 
use for wireless receivers. The receivers for radio pur- 
poses are made different than for ordinary purposes. 



Telephone Receivers for Wireless Receiving 253 

TELEPHONE RECEIVERS FOR WIRELESS 
RECEIVING 

Receivers for wireless purposes should be very sen- 
sitive. It has been found by experiments that the degree 
of sensitiveness depends largely on the frequency at 
which the received signals are sent. Thus, messages from 
a 900 cycle transmitter will produce an audible sound in 
the receiver when only 0.6 millionths of a voli is used, 
while impulses received from a 60 cycle set will only pro- 
duce an audible sound when 620 millionths of a volt are 
used. These figures are according to Dr. Austin, and 
while they are taken for a particular set of receivers, 
with the use of a laboratory arrangement, the general 
relation holds good. It is for this reason that the 
transmitters operating at 500 to 1,000 cycles are more 
effective than those operating at low frequencies. The 
sensitiveness of a given receiver depends on the fre- 
quency employed to operate it and also on the natural 
period of vibration of the diaphram. It is for this rea- 
son that thin diaphrams are employed in wireless re- 
ceivers. 

WHY A DETECTOR IS ESSENTIAL 

The detector (see Fig. 114), is not necessarily the most 
sensitive instrument at the receiving station, but is essen- 
tial because the telephone receiver, while more sensitive, 
will not of itself respond to high frequency oscillations 
such as are received at a wireless station. The reason 
should be apparent, for the change first in one direction 



254 Experimental Wireless Stations 

and then in the other, of the oscillations is so rapid that 
the successive changes neutralize each other and produce 
no effect in the receiver. To operate on these oscillations 
a telephone diaphram would have to move with frequency 
corresponding to approximately one-millionth of a sec- 
ond, which of course it cannot do. Again, we have seen 
that high frequency oscillations are greatly impeded by 
large inductance, so that the self inductance of the re- 
ceiver would prevent any except minute currents from 
operating it. The detector, then, translates the received 
oscillations into a current which will operate the receiver. 
The oscillations coming in on the aerial A, Fig. 114, are 
transformed by the detector into currents which operate 
the receiver. 

THE RECEIVED SIGNAL 

The received signal, then, is made up of wave trains 
which set up an oscillatory current in the receiving sta- 
tion which corresponds to that sent by the transmitter. 
When it is remembered that the transmitted energy is 
sent out in all directions it is remarkable that one point 
such as a receiving station receives as much energy as 
it does. According to Mr. Pickard, measurements of the 
maximum energy received from a high power transmit- 
ting station 90 miles away, showed this energy to be .03 
ergs per dot. The "erg" is equivalent to one ten-millionth 
of a watt. Inasmuch as a sensitive telephone receiver 
will operate with an audible sound on as little as one- 
millionth of an erg this leaves a considerable margin. 
In any case, the received energy is many hundred times 



Tuning 255 

the actual energy necessary to produce an audible sound 
in the receiver, but since the receiver will not of itself 
operate efficiently on the high frequency oscillations, the 
detector employed limits the efficiency of the receiving 
station to a large extent. 

Like other transformers, the detector represents a 
source of loss. The modern detector, however, is quite 
sensitive. 

Now the simple circuit shown in Fig. 1 14, comprises an 
untuned receiving set and is of little use without an 
auxiliary tuning apparatus if messages are to be received 
from modern transmitters. 

TUNING 

In order to receive signals from a transmitter, the 
receiver must be adjusted so that its circuits are in tune 
or resonance with those of the transmitter. Both the 
transmitter and receiving circuits must have the same 
time period of oscillation. Thus, if the receiver is to 
receive from a station sending out a 300 meter wave it 
must be adjusted so that its wave length is very nearly 
300 meters. However, if the transmitter is poorly tuned 
or very close to the receiver, it is a common occurrence to 
receive the message without careful tuning, or even with- 
out any tuning. The apparatus for tuning a receiver 
consists, as at the transmitter, of adjustable circuits con- 
taining variable capacity and inductance. 

The same receiving set may be used for either wire- 
less telegraphy or telephony, since the conditions are 
identical in many respects. Indeed, both telephone and 



256 Experimental Wireless Stations 

telegraph messages can be heard at the same time in some 
localities. 

The requisites for the receiver then are: 

1. Sensitive detector. 

2. Sensitive telephone receiver or recorder. 

3. Accurate auxiliary adjustable circuits for tuning. 

4. A good aerial and ground, as for the transmitter, 
or a coil as described in Chapter III. 

The several items will receive attention presently, in 
some detail. 



TABLE OF DETECTORS— SENSITIVENESS 

Type of Detector. Energy required to operate. 

in ergs, per dot. 

Audion (regenerative) 0001 f 

Audion (rectifier without feedback) .0003 t 

Electrolytic 003640 — .000400 * 

Silicon 000430— .000450 * 

Magnetic hysteresis detector 01 § 

Hot-wire barretter 0.08 § 

Carborundum 009000— .014000 * 

* According to Pickard. f Author's estimate accord- 

§ According to Fessenden. ing to adjustment. 



CHAPTER XVII 
Detectors 

Vacuum Tube Detectors; Solid Rectifiers; Crystals; Con- 
struction of Detectors; Crystal Mounting; Adjustments; 
Buzzer Test. 

Quite a number of different types of detectors have 
been discovered and developed and there are many forms 
for these. 

Vacuum tube detectors are at present the most sensitive 
and popular. There are many forms but the general 
type is in universal use. It consists of a lighted filament 
placed near a sheet electrode or plate with another elec- 
trode or grid interposed there between, the whole being 
in an evacuated bulb. These devices will be separately 
discussed. 

For experimental purposes, however, the types known 
as crystal or solid rectifiers are still valuable because of 
their sensitiveness, low cost, easy adjustment, portability 
and durability. Other forms which may be used are 
coherers, loose contacts, (almost any loose contact, as 
between a piece of carbon and a needle, being suitable), 
magnetic detectors, barretters or thermal detectors, elec- 
trolytic detectors, and gaseous detectors. 

257 



258 



Experimental Wireless Stations 



Solid rectifiers consist essentially of certain metallic 
compounds, such as oxides and sulphides, which have the 
property of rectifying the high frequency oscillations. 
That is, these metallic compounds when connected in a 
circuit, conduct the current better in one direction than 
in the other. This unilateral effect is quite marked, so 
that the detector acts as a valve, allowing the current 
to pass in one direction but preventing it from passing 
in the reverse direction. In addition it is necessary to 
have this rectifying effect carried on regularly so that the 
oscillations are rectified into a pulsating one way or direct 
current. 'The latter then serves to operate the telephone 



Mineral Name. 

Carborundum 

Fused Silicon 

Iron Pyrites 

Copper Pyrites 

Chalcopyrites 

Hessite 

Zincite 

Octahedrite 

Stibnite 

Galena 

Molybdenite 

Zirconium 

Niccolite 

Domeykite 

Sphalerite 

Pyrrholite 

Corundum 

Hematite 

Cassiterite 

Siderite 

Malachite 

Cerusite 



Chemical Name. 

Silicon Carbide 

Silicon 

Iron Sulphides 

Copper Sulphide 

Copper Iron Sulphide 

Telluride of Silver and Gold 

Zinc Oxide 

Oxide of Titanum 

Antimony Sulphide 

Lead Sulphide 

Molybdenum Sulphide 

Zirconium 

Nickel Arsenide 

Copper Arsenide. 

Sulphide of Zinc 

Iron Sulphide 

Oxide of Aluminum and Iron 

Iron Oxide 

Oxide of Tin 

Iron Carbonate 

Copper Carbonate 

Lead Carbonate 



Detectors 259 

or other recorder. The metallic compounds used have 
this property also, so that a solid rectifier is a good de- 
tector for the wireless receiving circuit. It is interesting 
to note that while a part of this phenomena was noticed 
as early as 1874, these metallic compounds were not 
understood and used as detectors until about 1906. A 
partial list of the elements and compounds which may be 
used for this purpose follows: 

With the exception of Carborundum these may all be 
used without a battery with good results. Usually a 
battery with potentiometer control is employed to adjust 
for the best portion of the detector's operating charac- 
teristic. When two different crystals are used together 
to form a pericon detector, the use of a battery is op- 
tional. 

In use, a small piece of the compound which will be 
hereafter called a crystal for convenience, is mounted 
between two metallic contacts. The exact nature of these 
contacts depends upon the particular crystal employed, 
and in nearly every case, it is desirable to make the con- 
tacts adjustable, so that the most sensitive part of the 
crystal can be used with the contacts at the best pressure. 
In practically every case it is desirable to make one of 
the terminals or contacts with a large area so that it 
makes very good contact with the crystal. This is to pre- 
vent the other contact from forming an opposing and 
undesirable second rectifier, which would greatly reduce 
the effect. The crystal then, is mounted between a large 
and a small contact. Silicon is perhaps one of the most 
widely used solid rectifiers. The iron pyrites or pyron 
detector, the galena or lead sulphide detector, and the 



260 Experimental Wireless Stations 

molybdenite detector, in the order named, are the other 
single crystal rectifiers in most general favor. Each has 
certain advantages and disadvantages and the various 
factors which determine the utility of a detector are so 
variable that direct comparison without exact tests is 
not possible. In order to secure the necessary large con- 
tact for these detectors, the crystal is imbedded in a cup 
with a fusible alloy such as Woods' metal, while the 
small point consists of a rounded adjustable point of 
brass, gold, platinum, or else a wire of these metals. 
When two or more of these crystals, one of which is 
preferably zincite, are used, this small metallic point is 
replaced by a fragment from another crystal. A small 
piece of chalco-pyrite is generally used for this purpose. 
This pericon detector is quite sensitive. Small metal 
points are most suitable for polished crystals such as 
iron pyrites and galena. These two detectors are par- 
ticularly free from injury from mechanical shocks or 
foreign electrical impulses. 

For experimental purposes it is well to provide what 
is known as a universal detector stand so that any or all 
of the materials as well as new ones as yet undiscovered 
may be tried. There are plenty of un found materials 
which may be much better than those now in use and a 
search for some of these would furnish enough excite- 
ment for the average experimenter for some little time. 
It is well to remark, however, that a mere duplication 
of detectors no better than those already in use will not 
be of much importance or use. What is wanted is some- 
thing better, more sensitive, having less resistance, and 
which is more reliable and permanent. Vacuum tubes 



Constructional Details 261 

of course accomplish these results very closely but they 
have their own disadvantages and can be improved. 

Even if a vacuum tube is to be used, a crystal detector 
is still a good auxiliary and can be relied on when the 
batteries of the tube circuits suddenly fail. 

CONSTRUCTIONAL DETAILS 

There are a great variety of constructions for solid 
rectifying detectors, almost every experimenter making a 
different kind or different form. Provided that the fol- 
lowing general requirements are adhered to, the matter 
of size, adjustment (mechanical movement used), and 
form is of little consequence. The reader has unlimited 
latitude and opportunity to exercise his ingenuity. A 
few accepted forms which are similar to those in general 
use are shown as examples. 

MATERIALS 

The crystals in general use can be had from supply 
houses. Whenever possible tested crystals should be pur- 
chased, as this saves considerable time and trouble. For 
instance, it may happen that only a dozen or so suitable 
points will be obtained after trying out a pound of ma- 
terial, broken up into points. The silicon used should 
be fused silicon, the carborundum preferably green car- 
borundum, and all of the others in the best grade obtain- 
able. Cheap grades generally contain considerable for- 
eign matter which is of course not desirable. Owing 
to the fact that the most commonly used crystals are 



262 



Experimental Wireless Stations 



mentioned in the claims of patents held practically by 
one holding company, many dealers in minerals and crys- 
tals do not sell them for fear of infringement suits. The 
various cups, brass, screws, and other materials can also 
be had from supply houses. 

Crystal mounting. Fig. 115 shows some suitable mount- 
ings for the crystals to form the large contact necessary. 
Two spring pieces fastened to a block of wood as at 
(a) will do. Perhaps the best mounting is that shown 
in the figure at (b), where the crystal is held in a cup 
containing a fusible alloy. This may be made by melt- 



CrysfaA, 



Spring 
Pieces -;' 




Base- 



Fig. 115. — Mounting for Crystals. 



ing four parts of bismuth, one part of cadmium, two 
parts of lead, and one part of tin together. Three parts 
of a good grade of solder may be used instead of the 
lead and tin. The melting point of this alloy is approxi- 
mately 138 degrees F, and this mixture is used so that 
the resulting heat will not injure the crystal as ordinary 
solder would. The cup should be well cleaned before 
pouring the alloy in and around the crystal. The metal 
is preferably poured into the cup and then the crystal 
is placed into the metal, and held in place until the alloy 
cools. A substitute for this method is to pack the crystal 



Materials 



263 



in the cup with tinfoil wads. This allows the crystal 
to be removed so that the sensitive part can be found. 
The cap from a round dry battery carbon can be used 
for a cup if it is well cleaned and polished. The tinfoil 
can be packed in so tight that the crystal will not fall 
out, and if the exposed part is found not to be sensitive, 
the crystal can be removed, turned over, and tried again, 
until a sensitive part is found. Many similar arrange- 
ments will suggest themselves to the reader. Almost any 
form of spring, clamp, or other contact which will make 
a large contact and hold the crystal in place is suitable. 
The crystal used should be a small fragment as it 
will then work as well or better than a large piece. It 
must not be ground and should be left in its natural 



Crystal 



Removable D/sc* 



=Q 



Fig. 116.— A Convenient Crystal Detector. 



shape. Most of the materials are best used as small 
chunks. Molybdenite is best used as a thin sheet. The 
molybdenite may be easily copper plated so that connected 
wires can be directly soldered to it. When a pericon set 
is used, the zincite should have a larger surface than 
the other crystal. The latter may be a fragment of bornite 
or chalcopyrite, preferably with a definite point for con- 
tact. 

In making a universal detector, it should be remem- 



264 



Experimental Wireless Stations 



bered that three types of contacts will be needed to in- 
clude suitable contacts for all materials. Crystals like 
silicon work best with a blunt point and light contact, 



Adjusting 
Screw— 



I Bed Plate, 

si *~ 



Contact 
\\\.--Spring 



-Knob 
"Standard 



Fig. 117.— An Adjustable Crystal Detector Stand. 

A 



m 



22j. 



M5 



Fig. 118.— A Compact Crystal Detector. 

#8-32 Thds., B; {Spring ,__, 

Q 




,'Ball 



Soldered-. 



A* K 






Brass 
Strip— 



Fig. 119.— A Universal Detector. 



molybdenite with a blunt point and comparatively heavy 
contact, those like galena and iron pyrites require a fine 
light point, and others like carborundum require two large 
contacts with a comparatively large pressure. An ar- 



Materials 265 

rangement which will provide for these variable condi- 
tions is, therefore, desirable. Some suitable mechanical 
arrangements are shown in Figs. 116, 117, 118. In the 
clamp type, the crystal can be removed and another one 
replaced, while in the multi-crystal type the several crys- 
tals are mounted so that any one may be used at a time. 
Where compactness is no object it is perhaps a better 
plan to have a plurality of separate detector stands for 
each crystal. A duplicate detector is also desirable, so 
that when one crystal becomes poorly adjusted, another 
sensitive detector can be immediately switched into cir- 
cuit. 

Referring to the figures, which were collected from 
various sources, Figs. 116, 117, 118 show suitable con- 
structions for a simple universal detector and require no 
further comment. In Fig. 118, A represents an insulated 
thumbscrew, B a brass spring strip, C a metal standard 
of round or square brass, D. F. G. contacts which may 
be used for a variety of materials, H a base, I a brass 
strap, and J a notched cup. 

Fig. 119 shows another universal detector. The shaft 
A slides into a ball B, which is in turn held by the strips 
A 1 with a pressure adjustable by F. The spring S keeps 
A in position. C is a simple screw chuck holding another 
chuck D in which a point is in turn held. Different shaped 
points may be used in this manner. The crystal is held 
adjustably in a clamp A2. The arrangement is quite 
simple and allows almost any desired adjustment and 
use. 

The multi-cup arrangement of Fig. 120 is taken from 
patent No. 1,027,238, and is quite simple. The post C 



266 



Experimental Wireless Stations 



can be turned so that the contact G makes contact with 
any one of the cups arranged as a circle on the base. 
The contact G can be reversed so that the detector can 
be used as an electrolytic detector with one of the cups 
K. The spring I provides a mild, variable pressure, and 
the rough adjustment is made by the screw F clamping 
E to C after the proper length has been found. Fig. 121 



Adjustable Screw, 




EE3 




Spring- 




Hard Rubber 



Nut.J 



Wood 'Base 



•Nut 



Figs. 120, 121, 122, 123.— Crystal Rectifier Detector Details. 



shows a simple arrangement suitable for galena, iron 
pyrites and silicon, and needs no further comment. 

Fig. 122 shows a delicate adjustment suitable for the 
small movable point of a universal detector. Fig. 123 
shows a novel scheme for adjusting the pressure of the 
small point on the crystal. The piece B is mounted on a 
pivot so that it balances nicely. The pressure on the 
small contact can then be varied by screwing the nut 



Care and Adjustment 267 

A in or out, thus securing more or less weight on the 
fine point. Pericon crystals may be similarly mounted, 
the extra crystal replacing the fine point. 

CARE AND ADJUSTMENT 

Detectors should be regarded as sensitive and deli- 
cate instruments. They should be kept out of the sunlight, 
away from dust, dirt and acid fumes, and similar places. 

The crystals become less sensitive after a time, but 
can often be renewed by cleaning with gasoline or carbon 
bisulphide, using an old tooth brush and taking great 
care to avoid a fire or even a burning light, because both 
materials and particularly the bisulphide are very explo • 
sive. Heat alone if applied rationally will often restore 
an old crystal to sensitiveness again. 

BUZZER TEST 

The actual adjustment is a matter which must be 
determined by experiment. A buzzer test is very valu- 
able for this purpose and should be a part of every wire- 
less receiving set. This is simply a common buzzer, such 
as may be had for about 25 cents, connected to a key 
and battery and to a short aerial wire as shown in Fig. 
124. The wire need only be a few feet of number 18 bell 
wire. The connections can be arranged on the aerial 
switch so that when the switch is set for receiving, the 
transmitting key will operate the buzzer instead of the 
transformer. The noise of the buzzer should be 
deadened by covering it with old clothes or else by plac- 
ing the buzzer outside of the building, since it is not de- 



268 



Experimental Wireless Stations 



sirable to hear the buzzing sound. This buzzer sets up 
weak wireless waves and the detector is in adjustment 
when the said waves are received and heard the loudest. 
The short wire can also be directly connected to one 
terminal of the detector if desired but this is not recom- 
mended. Adustment of the detector may also be carried 
out while receiving from another station, provided that 
the copying of the message is of secondary importance 
while the adjustment is being carried out. Another suit- 
able circuit is readily made by connecting the condenser 



Buzzer^ 




Fig. 124. — Arrangement of a Buzzer Test for Detectors. 



terminals of a wave meter to the short wire and battery 
respectively. The turning on and off of an electric light 
socket can also be used as a buzzer test, the resulting arc 
supplying the necessary waves. While we are on this 
subject it may be noted that a lamp on a lighting circuit 
near the transmitting station can be made to light up 
when the station is sending. Turn the lamp on and then 
unscrew the bulb until it just goes out. The transmitter 
will then cause it to light, when the key is pressed. This 
experiment illustrates the coherer principle to a certain 
extent and will only work when the light is in close 
proximity to the transmitter. 



CHAPTER XVIII 
Sensitive Indicators for Receiving Sets 

Telephone Receivers; Continuous Wave Detectors; Ein- 
thoven Galvanometer; Construction of Indicators; Auto- 
matic Indicators; Hoxie Photographic Recorder; Ampli- 
fiers; Microphone Amplifier; Baldwin Receiver; Adjust- 
ments; How Receiver Operates; Measuring Intensity of 
Received Signal; Audibility Meter. 

In order to receive from a continuous wave transmit- 
ter such as a telegraph transmitter operated by an arc 
generator, which is not audibly altered at the transmitter, 
it is necessary to modify the received impulses audibly 
at the receiver. The human ear can only hear or recog- 
nize vibrations which do not exceed 35,000 or 40,000 per 
second, so that the waves sent out from an arc generator 
vibrating at many times this rate are inaudible. One 
form of indicator which will efficiently record such in- 
audible waves without modifying them at the receiver 
by a vibrator or chopper is the Einthoven galvano- 
meter. While this is a delicate instrument, a brief ac- 
count of it will be given so that it may be constructed 
by skilled workers. 

269 



270 



Experimental Wireless Stations 



EINTHOVEN GALVANOMETER 

This instrument consists essentially of a fine wire 
stretched between the pole pieces of a powerful electro- 
magnet. This wire may be of platinum, silver, aluminum, 
or copper, and should be very fine. No. 40 or 50 such as 
is used for telephone receivers can be used. The con- 
struction and arrangement is shown in Fig. 125. In the 

I. 




FlG. 125. — Einthoven Galvanometer Details. 



most sensitive forms, a thin quartz or glass fibre which 
has been platinized is used and the reader is advised to 
purchase it from a supply house. The fine wire is 
mounted on T shaped set screws C and F, so that the 
tension can be delicately adjusted. As shown, this is 
accomplished by having C attached to a rod having a 
cam K on its upper end and held in place by a spring L. 



Einthoven Galvanometer 271 

When the lever Ki presses down on the rod, a very fine 
adjustment is secured. Ki is operated by a micrometer 
screw J, as shown. A more simple arrangement would 
also do, but the adjustment would then be less accurate, 
and more difficult to carry out. 

The smaller part of the figure shows the position of 
the wire and magnets and one method for observing the 
displacement of the wire. The eye piece AE is inserted 
in a hole in one of the magnet poles.* Light is pro- 
jected by the tube C and lens F. When the current flows 
in the direction of the arrows, the wire stretched between 
CC has a deflection indicated by the arrow a. This dis- 
placement can be magnified by projection upon a screen, 
in which case the eye piece is removed and a strong 
light applied at C. This recorder is very sensitive and 
can be used for long distance work as well as for ex- 
perimental measurements. The amount of deflection in- 
dicates the strength of the received signal. In practice, 
a photographic record is taken by means of a moving film, 
so that a permanent record of the message as a defined 
line according to the dots and dashes, is the result. The 
experimenter may dispense with the photographic record. 
The skilled reader should not find it difficult to make a 
duplicate from this brief description. The magnet used 
should consume about 250 to 500 watts, and ready wound 
magnet coils may be pressed into service for experimental 
purposes. The success of the instrument depends on the 
fact that the fine wire has a rapid period. The instrument 
will not be of any use, however, unless delicately con- 
structed. 

* Old microscope parts can be used. 



272 Experimental Wireless Stations 

AUTOMATIC INDICATORS 

Other sensitive recorders have been developed but re- 
quire expert manufacturing facilities to produce. Sig- 
nals received from stations several thousand miles away 
can be continuously recorded today by photographic or 
sound recording machines. The phonograph and tele- 
graphone have been used successfully for short distance 
recording. 

HOXIE PHOTOGRAPHIC RECORDER 

A photographic recorder which can be connected in paral- 
lel to the telephone receivers in an ordinary amplified radio- 
receiver has been developed by C. A. Hoxie and it has been 
the author's privilege to make extensive pioneer use of this 
sensitive device. 

A wee-bit of a mirror is mounted on knife edges and con- 
nected by a mechanical advantage whisker to a strip dia- 
phram similar to a telephone receiver diaphram. This strip 
diaphram is arranged so that its tension can be adjusted for 
response to different frequencies. Suitable magnet coils are 
arranged about the strip so that a slight movement is imparted 
thereto when audible group frequency flows in the coils 
from the detector-amplifier. This slight motion is mechan- 
ically amplified to vibrate the mirror. A spot of light from 
a tungsten bulb falls on this mirror and is thereby caused to 
move up and down on a strip of sensitized photographic 
paper which is driven by clockwork or an electric motor. 
The strip is automatically developed as it passes through 
suitable treating baths. Messages at as high a rate as 600 
per minute can be recorded so that mechanical secrecy in 
communication is now feasible, it being impossible to get 
such intelligence with an ordinary receiver. The apparatus, 
while not as sensitive as a telephone receiver, -works nicely 
on an audian amplifier so that long-distance signals are 



Hoxie Photographic Recorder 273 

readily recorded. The device is not simple enough for ama- 
teur duplication at present so construction details are not 
given here. 

In order to receive unaltered continuous waves with 
an ordinary wireless telephone head receiver, the received 
impulses must be modified, interrupted or chopped. This 
can be done by the arrangement of Fig. 126, in which the 
relay shown is a 20 ohm or 75 ohm telegraph relay, hav- 
ing its magnet connected to an alternating current line 
through a lamp. The secondary platinum terminals are 



Wa 



€ 



■fhtcl VrY D 
, IT 



f 1 



Simpk 

fl 




1 fr w " 

=j=C falay-.S 
I kflBHE> • •T • ' 



* fa fay 



Fig. 126.— Poulsen "Tikker." 



used to alternately connect and disconnect a large fixed 
condenser in the receiving circuit as shown, thus balanc- 
ing and unbalancing the circuit at an audible frequency so 
that the received signals are rendered audible. This ar- 
rangement also effectually cuts out a great deal of other 
interference. When ordinary stations are to be heard the 
relay is merely disconnected from the line. The re- 
mainder of the circuit is familiar or will soon be and 
needs no further comment. The relay acts as an inter- 
rupter and may be used to throw either capacity or in- 



274 Experimental Wireless Stations 

ductance or both in and out of the circuit. The insert 
shows a simple method for the same purpose. In this 
case a single condenser is used in shunt about the tele- 
phone receivers. The remainder of the circuit is not 
shown as it is the same as before. 

Either the Einthoven galvanometer or this chopper 
arrangement will be satisfactory to detect the continuous 
waves. With this arrangement, experimenters may re- 
ceive from the Poulsen arc stations provided that the cir- 
cuits are properly tuned. In connection with the ap- 
paratus described in Chapter XIII for telegraphy with- 
out modifying the continuous waves at an audible fre- 



fnc/uction Co/'l^ 
Telephone i . | . i , \, Output, 

Receiver, 





'Carbon Grains""^ 
\ Carbon Electrodes' 
^Soldered to Diaphram 

Input 
Fig. 127. — Microphone Amplifier. 

quency at the transmitter, this form of detector forms 
an ideal one for the experimenter who does not wish to 
use vacuum tubes, but the latter are superior and more 
desirable. A somewhat similar arrangement is some- 
times incorporated directly in the detector or condenser 
C (which latter is rotated by a motor), but since it is not 
much better, it will not be described here. 



Other Amplifiers 



275 



OTHER AMPLIFIERS 

Brown's microphone relay has found slight use. It 
is connected in place of the phones and amplifies through 
a microphone contact which controls a local circuit. The 
telefunken amplifier is similar but employs a number of 
such telephone-transmitters of special reed type in cas- 
cade so that the amplified current of one circuit actuates 
the next, etc. A similar device employing a liquid micro- 
phone instead of a contact device has been brought out 
by L. Bishop and a few are in use. Microphonic ar- 

Illh 



4± 




3Q 



G turns, No. 34 Ou tpuf.' 

Resistance Wire Heated 



■Telephone Receiver 

' ■*■ input 

' Small 2"Dia. Motor driven air pump 

Fig. 128.— Hall Jet Amplifier. 



rangements give amplifications of 20 upwards but are 
difficult to keep in adjustment and in general unreliable. 
Various microphonic amplifiers have been used for 
experimental radio work. A readily constructed form is 
shown in Figure 127. A. valuable air jet type amplifier 
is shown in Figure 128. A continuous current of air is 
passed through an enclosed electrically heated spiral of 
resistance wire. Another fine needle jet closely at right 



276 



Experimental Wireless Stations 



angles thereto is acoustically connected to the receiving 
telephone and modifies the air jet and hence the resistance 
of the wire spiral, the changes of which are repeated as 
an amplified output. Some mechanical amplifiers have 
also been used experimentally. The electron tube ampli- 
fying circuits are best for most purposes. 

TELEPHONE RECEIVERS 

Fig. 129 shows telephone receivers used in radio work. 
The Baldwin type magnifies the motion. The monotele- 
phone can be adjusted to respond best to a definite 
audible group frequency. 

Ordinary telephone receivers may be used as recorders 



Permanent hard 
steel magnets 




\ /Binding Post 



Electromagnet 
Coils 



Ordinary Receiver 




Mono+elophone 
(Tuned Receiver) 



Steel Soft Iron 

Magnet* , pole -pieces 




■ Connecting L ink 
to Diaphram 



*~Soft Iron 



Baldwin Receiver 

Fig. 129. — Telephone Receivers for Radio Service. 



Telephone Eeceivers 277 

for experimental work over short distances, but specially 
constructed wireless receivers are necessary when long 
distance work is to be done. The receivers in general 
use are of the watch case type and either one or two 
receivers on a headband may be used. Since most people 
are able to hear much better with one ear than the other, 
it is an advantage to use only one receiver on the head- 
band and to block off the other ear from foreign sounds 
by a rubber pad. This method is less expensive than 
when two receivers are used on a headband. However, 
if two receivers are used they must be identical in their 
dimensions and windings as otherwise the one having the 
least resistance or other unequal dimension will not work 
in accordance with the other one. Many manufacturers 
are now making reliable light weight receivers suitable for 
the most exacting wireless work, and while the latter are 
perhaps a little expensive, they are essential to efficient 
work, particularly over long distances. The reason why 
a low resistance telephone receiver such as is used for 
telephone work is not suited for delicate wireless work 
is that it is made to give a loud response with a com- 
paratively large amount of applied energy but will not 
give any response with very minute currents, such as are 
produced by a detector receiving from a distant station. 
An ordinary receiver can be rewound, however, with 
No. 40 or 50 enameled wire so that its utility will be 
much greater. When this is done a new and thinner 
diaphram should also be supplied, since the ordinary 
diaphram is too thick for wireless purposes. These thin 
diaphrams may be had at supply houses and some are 
known as gold diaphrams because they are gold plated. 



278 Experimental Wireless Stations 

A wireless receiver is not intended to give a loud re- 
sponse, but rather to give an audible and working 
response with very feeble currents. The resistance, how- 
ever, is not the. real delicate part of the receiver, and 
the mere statement that a receiver is wound to 1,500 
ohms means little or nothing. What is desired is a large 
number of ampere turns, and since this is best secured 
by using fine copper wire, No. 38 or 40 is generally em- 
ployed. Receivers are rated according to their resistance 
largely because this is a convenient measure, but as far 
as workability is concerned, the number of ampere turns 
is the essential factor which determines the actual utility. 
In any case, a resistance of over 1,500 ohms is no ad- 
vantage, and a resistance of less than 800 ohms is not 
desirabfe when the receivers are to be used with solid 
rectifying detectors. For vacuum tube detector circuits, 
1,500 ohm receivers are suitable. 

The author finds it advantageous to use a large 
telephone condenser in series with the telephone re- 
ceiver so that much or all of the inductive impedance 
of the telephone receiver is neutralized by the capacity 
reactance of the condenser. 

CARE AND ADJUSTMENT 

While a receiver seldom requires attention after it 
has been adjusted, it should be kept clean, and free from 
dust and moisture. When rewound receivers are used 
it is sometimes necessary to adjust the distance of the 
diaphram from the poles. This can be done by using 
a soft rubber cushion between the cap and the receiver 



Care and Adjustment 279 

case, and screwing the cap on with more or less pressure, 
thus adjusting the distance between the diaphram and 
the receiver's magnet pole. After long use, the perma- 
nent magnets should be tested and if the magnetic at- 
traction is weak, the magnet should be strengthened by 
remagnetization. A common test is to judge by the dis- 
tance between the receiver case and diaphram, which is 
necessary just before the diaphram (previously removed 
and laid on a table), is attracted to it. 

Receivers are seldom burnt out. This may be the 
case after a station has been subjected to a heavy static 
or lightning discharge. This can be obviated by shunting 
the receiver or the whole receiving set with a pin gap or 
lightning arrester. The headband used should be com- 
fortable and should keep the receiver tight against the 
ear. The receiver is very important and its sensitive- 
ness together with the hearing ability of the operator is 
one of the largest factors which determine the receiving 
range of a station. 

A word concerning standard receivers for wireless pur- 
poses. The magnets should be permanent and preferably 
of the consequent pole type, to prevent leakage about 
the pole pieces. The diaphram should be thin and uni- 
form, but of sufficient thickness to absorb sufficient mag- 
netic flux. The poles, case, and diaphram should be pro- 
portioned and made so that the maximum sensitiveness 
and least liability to injury and change is the result. 
Lightness and a good fit are important items as far as 
comfort is concerned, and if the receivers are to be used 
continually, this is a very important consideration. A 
suitable size for the wire used in the coils is No. 40 or 



280 Experimental Wireless Stations 

wire .0031 thick. A standard thickness for the diaphram 
is .004 thick exclusive of the plate or varnish coat, which 
last is to prevent rust and corrosion. 

HOW THE RECEIVER OPERATES 

It is well known to the readers that the telephone 
receiver depends upon simple magnetic phenomena, so 
an account of the action will be dispensed with. It is 
well to understand the action in a wireless receiving set. 

We have seen that the detector rectifies the oscilla- 
tory current into a pulsating direct current. Now, this 
direct current passes through the windings of the re- 
ceiver and causes the diaphram to be pulled according 
to the strength and changes in the current. While the 
current supplied to the telephone may have as much 
as a million pulsations in one second, the ear only hears 
a sound similar to that produced by a steady current 
on account of the regulation exerted by the inductance 
of the windings of the receiver. That is, each complete 
wave train after being rectified by the detector causes 
only one pull on the diaphram, so that the operator hears 
one sound corresponding to each transmitted wave train. 
The argument is similar in the case of vacuum tube cir- 
cuits. However, a complete signal, even a dot, generally 
comprises several successive wave trains so that the re- 
ceived signal is heard as a succession of clicks corre- 
sponding to the spark rate and speed at which the 
message is sent. The receiver gets the message almost 
the same moment that it is sent, since the waves travel 
at the rate of 186,000 miles per second, and the frequency 



Measuring the Intensity of the Signal 281 

tone, wave length and other variable factors are prac- 
tically the same as when the impulses leave the trans- 
mitting aerial. 

MEASURING THE INTENSITY OF THE 
SIGNAL * 

For experimental work it is often desirable to com- 
pare the relative strengths of the signals received either 
from two stations or from the same station using differ- 
ent instruments or circuits. A suitable simple arrange- 
ment for this purpose is shown in Figure 130, and con- 
sists simply of a calibrated shunt resistance about the 
phones. A non-inductive resistance box is suitable. The 
value of the received current in the telephone receiver 

Adjustable^ 
Resistance \ 



Fig. 130.— Shunt Audibility Meter. 



is practically proportional to the energy of the incoming 
waves so that a rough table of values based on audibility 
is easily made. Thus a station which produces a sound 
just audible in the receivers when all the resistance is in 

* This method can also be used to eliminate interference 
from weak stations, but is carried out at the expense of a 
decrease in the intensity of the received signal. It can, how- 
ever, be utilized in connection with a wave meter. 



282 Experimental Wireless Stations 

circuit may be taken as a standard. If another station 
just produces an audible sound when one-half of the 
total resistance is in circuit, the new value can be com- 
pared with the standard. The calibration could just as 
well be the other way around so that the standard is 
audibility with no shunt resistance. The result is best 
expressed as a fraction of or so many times audibility, 
as the case may be. 

Audibility is not an exact measurement because it de- 
pends upon human hearing ability which is variable. 

Actual telephone current 
Audibility = 



Least audible telephone current 
Z,+S 



s 

S == non-inductive shunt resistance 

Z t = resistance of telephone receiver if X is neglected. 

(Some audibility meters are corrected for X, the inductive 
reactance.) 



CHAPTER XIX 
Tuning and Interference Prevention 

Principle of Resonance Used in Tuning; Interference; Miti- 
gating Various Kinds of Interference ;• Tuning Methods; 
How to Tune a Receiving Set; Receiving Circuits; Loose 
Coupled, Bridge, and Interference Mitigating Circuits; 
How to Qse a Loose Coupler; Balancing Out Powef 
Line Hum. 

If the reader will bear in mind the discussions given 
for resonant circuits at the transmitting station, the re- 
quirements for tuning at the receiving station will not 
be difficult to understand. The two circuits are in fact 
quite similar in some respects. The detector corresponds 
to the spark gap. As in the case of the spark gap the 
detector's resistance damps the oscillations and makes 
sharp tuning difficult. The resistance of the detector, 
then, prevents absolute tuning. As far as the rest of the 
apparatus and circuits are concerned, absolute tuning can 
be very nearly reached if desired. Now, the tuning appa- 
ratus and circuit to, employ for experimental purposes 
will vary with the local conditions. In cities like New 
York, where the interference is considerable, very sharp 

283 



284 Experimental Wireless Stations 

tuning is desirable at both the transmitter and receiver, 
while in localities where there are only a few scattered 
stations, simple circuits with rough tuning will suffice, 
so that the intensity of the signal is about all that needs 
attention. In most of the present tuning methods, fine 
tuning is carried out at the expense of the intensity of 
the received signal, but for practical purposes all that 
is needed is a distinct audible signal. Close tuning has 
one disadvantage in that a message can easily be missed 
if the apparatus is at the wrong adjustment. In arranging 
a receiving set it is well to bear in mind the use to which 
the apparatus is to be put and to provide for the design 
accordingly. An ideal set, in the author's opinion, is one 
which provides two standby points and a variable close 
tuning or non-interference arrangement. One of the 
standby adjustments is for the standard 200 meter ex- 
perimental wave length and the other adjustment is for 
the standard longer wave lengths which one wishes to 
intercept for time signals or practice. After the message 
has started, any interference which may arise or be in 
progress can then be tuned out or dissipated by the sharp 
tuning adjustments. There are several arrangements 
which will give this ideal outfit and the parts will be 
described in some detail later. For the present, a close 
attention to the theory is of first importance. 

In localities where there is little or no interference, 
elaborate short wave receiving apparatus is not necessary 
or even desirable. Aside from the extra expense, the 
complicated receiving circuits involve greater skill and 
require more experience to operate. Experimenters 
should spend much more time tuning the transmitter 



Interference 285 

than in tuning the receiver, in most cases, as the former 
is really more important and instructive. 

INTERFERENCE 

If there was no interference in wireless work, all that 
would be necessary at the receiving station is a simple 
inductance with which to alter the receiving wave length 
so that the receiver can be brought into resonance with 
the transmitter. As it happens, however, the average 
station must be designed to work through both natural 
and artificial interferences. It may be explained that the 
term "interference" includes all foreign disturbances 
which impede or interfere with the regular reception of 
a desired message. 

NATURAL INTERFERENCE 

Mechanical vibrations, waves received from street arc 
lights, induction from power and telephone lines, static 
and similar disturbances are natural causes of inter- 
ference and can be overcome in nearly every case by the 
use of proper circuits. A looped aerial is best to adopt 
when these disturbances are particularly marked. With 
the exception of strong disturbances, these natural dis- 
turbances can be controlled and either dissipated or 
neutralized. Experimenters are advised to abandon the 
use of the aerial during local electrical storms. Although 
the use of short aerials of low height does not ordi- 
narily mean a liability to much danger, it is well to be on 
the safe side. Mechanical vibrations can be taken up by 



286 Experimental Wireless Stations 

using cloth or rubber pads on the instruments. A small 
multi-turn indoor receiver is usually safe to use, even 
during a storm. 

ARTIFICIAL INTERFERENCE 

This is the form of interference resulting from reg- 
ular wireless communication between several stations 
within the range of each other. The manner of over- 
coming this to a large extent, by the use of resonant 
transmitters having definite wave lengths, has already 
been pointed out in detail. If every station (this means 
both commercial and experimental) would use just 
enough power to transmit to the desired station, sharply 
tuned resonant circuits, a definite wave length and "wire- 
less sense," the difficulty of the problem, even with simple 
instruments of the present design, would be much re- 
duced. Phase tuning is also coming into some use, as 
described in Chapter XX. 

In its average or worst form, artificial interference 
means working through from four to a dozen or more 
other stations, simultaneously sending at approximately 
the same band of wave lengths and same intensity. The 
operator who receives, however, cannot regulate the 
coupling or adjustments of the several transmitting sta- 
tions and must accept conditions as they exist. The sev- 
eral items must be successfully met and the interference 
dissipated without losing the desired message. While this 
is not always possible, it can generally be approximated. 
The worst item to overcome is the matter of forced 
waves, or those which seem to come in at every wave 



Tuning Methods 287 

length on account of the proximity and heavy coupling- of 
the transmitter. When the interference prevention meth- 
ods to be described are employed, these forced wave dis- 
turbances can be practically eliminated in nearly every 
case. While the use of limited or restricted waves will 
prevent interference between commercial and experi- 
mental stations, the experimenters must still fight it out 
among themselves. In some respects short wave lengths 
are less immune from interference than the long wave 
lengths. If only undamped waves were universally used 
and vacuum tube beat receivers employed, several hun- 
dred stations could work close together without inter- 
ference. However, the experimenter may receive from 
any and every station within range without difficulty, if 
the simple relations of a tuned receiving set are under- 
stood. 

TUNING METHODS 

It must be remembered that the ordinary station emits 
at least two defined wave lengths. The sharper the two 
are defined, the better as far as the receiving operator 
is concerned. See diagrams in Chapter V. With 
quenched spark or arc stations sharply tuned, practically 
a single sharp wave length is all that needs to be con- 
sidered, but interference from other stations operating 
at the same wave length often complicates the matter. It 
may be stated right now that the number of possible 
connections for the receiving circuit is practically un- 
limited, but that many so called hook-ups are a mere 
duplication for old circuits and really accomplish noth- 



288 Experimental Wireless Stations 

ing. In building and arranging the apparatus for the 
receiving circuit, the actual factors concerned and the 
remedies should receive attention rather than a hit and 
miss elaboration of the circuits without conforming to 
the requirements. Bearing in mind that tuning the re- 
ceiver means nothing more or less than altering the 
circuits by adjusting the amount of capacity and induc- 
tance used, (resistance is also a factor), the following 
summary will aid in designing a receiver. 

FACTORS AND REQUIREMENTS FOR TUNING 
THE RECEIVER 

1. Close coupling at the receiver should be used when 
the transmitter is close coupled and vice versa. 

2. With the receiver tuned to the desired transmitter, 
a large amount of the disturbance can be eliminated by 
reducing the coupling, until the strength of the signals 
is just distinct. 

3. A shunt resistance as described in Chapter XVII 
may be used as a substitute for or in addition to meth- 
od 2. 

4. The two wave lengths sent by a spark transmitter 
being designated as short and long, tuning for either the 
long or the short wave (detuning) to an extreme degree 
is often a marked advantage. Since the short wave is 
generally the least desirable, the aerial circuit of the 
receiver is best thrown out of tune on the short wave 
side as much as is possible. 

5. When the desired message comes in quite loud, 
the insertion of some resistance directly in the aerial cir- 



Requirements for Tuning the Receiver 289 

cuit will often cut out disturbances, but at the expense of 
the intensity of the signal.* 

6. In tuning, remember, that an inductance in series 
with the aerial or a capacity in shunt with a series in- 
ductance in the aerial circuit, increases the receiving 
wave length. A series capacity in the aerial circuit on the 
other hand, decreases the receiving wave length. 

7. A closed or looped aerial will eliminate many of 
the natural disturbances. (See Chapter III.) 

8. The disturbing impulses can be made to oppose 
and neutralize each other, while the desired signal, (at 
a reduced intensity), is received. (Differential method). 
(Bridge method). This is a very desirable method, and 
if the waves are in a sufficiently long train, it is possible 
to discriminate between them and undesired impulses. 
If the undesired impulses are more rapidly damped than 
the desired impulses they can be avoided, even when they 
are of the same period as the desired waves, under favor- 
able conditions. 

We shall now discuss some examples of approved cir- 
cuits embodying the above principles, starting with the 
more simple ones. See discussion of Vacuum Tube Cir- 
cuits for more advanced examples. As has already been 
stated these may be varied almost at will, the essential 
forms being given wherever practicable. While a brief 
outline of the operation will be given, a close study of 
the diagrams will be ,.ecessary. The numbers which 

♦About 5000 ohms will usually prevent reception of any 
signals and very few strays. See British Pat. 101,540 for a 
proposed scheme based on this. 



290 Experimental Wireless Stations 

follow do not correspond with the numbers for the fore- 
going summary. 

CRYSTAL DETECTOR CIRCUITS 

1. Fig. 131. Simple tuned circuit with wave length 
varied by adding more or less inductance to the antenna. 
The particular inductance indicated is known as a single 
slide tuner. The condenser in shunt about the detector 
increases the intensity of the received signal. While 
desirable, it may be dispensed with for short distance 
receiving. The coupling is fixed in this arrangement and 
while it is useful to bring a station to approximate reso- 
nance with the transmitter, close tuning or prevention 
of interference is not possible. In this and other dia- 
grams the letter A denotes the aerial, G the ground, D 
the detector, C a fixed condenser, T the receivers, and 
L represents the inductance. 

2. Fig. 132. Same as before, except that a shunt 
variable condenser VC is provided. An increase of ca- 
pacity of VC increases the wave length. 

3. Fig. 133. Double slide tuner. Coupling of the 
circuit can be changed, but must be relatively close. De- 
sirable where little interference is met with. 

4. Fig. 134. Three slide tuner. Same as before, ex- 
cept that the coupling of the aerial and detector circuit 
can" be varied to a larger extent. The position of the 
two circuits can be varied. Thus with the sliders in- 
cluding the detector circuit remaining a uniform distance 
apart, they can both be shifted up or down the turns of 
wire, while the ground slider remains fixed or also be- 



Crystal Detector Circuits 



291 



comes changed. The relative positions of the aerial and 
detector circuits can thus be changed. The desired ad- 



V 



V' 



L £ — I 

— I— r D 



V.C. 



* 






Figs. 131, 132.— Detector Circuits. 



D- 




Figs. 133, 134.— Crystal Detector Receiving Connections. 




Fig. 135. — Bridge Receiving Circuit. 



292 Experimental Wireless Stations 

justment can only be found by trial and when once found 
should be noted before changes are made. 

5- Fig. 135. Bridge. Three slide tuner with the de- 
tector circuit shunted around the terminals of the wire. 
Four or five slides would be better to use. When both 
branches of the divided circuit are maintained in a sym- 
metrical condition the received impulses are equally 
divided so that they have no effect on the detector. The 
arrangement is like a Wheatstone bridge, the detector 
corresponding to the galvanometer. Now, to receive the 
desired signals, the ground contact is shifted to the right 
or left until the best position for the desired impulses is 
found. (See 8 of the foregoing summary.) 

6. Fig. 136. Loose coupler, LC. Sharp tuning is 
possible because the coupling can be greatly varied. This 
is a very popular form of tuner, and while it derives its 
name from the fact that the secondary can be pulled 
away from the primary, the heaviest coupling is reached 
when the middle of the active primary turns is directly 
over the middle of the active secondary turns. When the 
sliding secondary is inserted farther in the primary after 
this point has been reached, the coupling again becomes 
loose. Since this form is best adopted as a standard be- 
cause of its utility and comparative simplicity, its rela- 
tions and peculiarities will be more fully described. The 
following summary by M. O. Andrews is of interest in 
this connection. 

"1. Increasing the inductance of the primary increases the 
long wave length rapidly, but the short wave length is in- 
creased so slowly that it may be considered as remaining 
constant. The opposite is true when inductance is taken 
from the primary. 



Crystal Detector Circuits 



293 



2. Increasing the inductance of the secondary increases 
both the long and the short wave lengths equally, or nearly 
so, and vice versa. 

3. Loosening the coupling between the primary and sec- 
ondary decreases the long wave length and increases the 
short wave length. Tightening the coupling increases the 
long and decreases the short wave lengths. In other words, 
its action is the same as the oscillation transformer of the 
transmitting set. As the coupling is loosened the two wave 
lengths approach the wave length to which each circuit is 
individually tuned, and as the coupling is closed the two 
wave lengths are driven farther from the natural wave 
length of the circuits. 

4. Increasing the capacity in the primary circuit increases 
both wave lengths, and vice versa. 




Fig. 136. — Loose Coupled Receiving Circuit. 



5. The variable capacity in the secondary circuit is used 
principally to put the secondary in resonance with the pri- 
mary, thereby allowing looser coupling than would other- 
wise be possible. This allows atmospheric disturbances to 
be cut out to some extent without decreasing the audibility 
of the signals. 

We have already observed that it is possible to hear a sta- 
tion radiating a double wave at two places on our tuner. In 
one case, we are in tune with the long wave and in the other 
with the short wave. We may also be in tune with both the 
long and the short waves at the same time. This is a de- 
cided advantage, as we will then receive energy from both 
waves, and the signals will consequently be much louder 
than when tuned to only one of the waves. 



294 Experimental Wireless Stations 

How may the different types of interference be avoided? 

Case i. When in tune with the long wave length of the 
damped wave transmitting station, there are four principle 
types of interference that we must dodge. 

1. Another station may commence sending, whose long 
wave is of the same length as the one which we are receiv- 
ing, but whose short wave is either longer or shorter than 
the short wave of the station from which we are receiving. 
For instance, suppose we are receiving from a station radiat- 
ing waves of 1,500 and 500 meters respectively. We are 
tuned to 1,500 and 400 meters, and another station com- 
mences sending using waves of 1,500 and 600 meters. By 
referring to the effects of coupling on double waves we find 
that this type of interference may be tuned out by simply 
loosening the coupling which lowers our long wave length 
perhaps to 1,300 meters and raises our short wave length to 
500 meters. The desired signals will then come in not on 
the long wave, but on the short wave, where there is no 
interference. If the coupling is loosened too much our short 
wave length will be raised to 600 meters, where the unde- 
sired signals will again be picked up. 

2. While we are still tuned to 1,500 and 400 meters, and 
are receiving from a station radiating waves of 1,500 and 500 
meters, another station may begin sending, using a short 
wave of 400 meters and a long wave, either longer or shorter 
than 1,500 meters. It may be tuned out by adding capacity 
to the primary circuit, which increases both wave lengths to 
1,700 and 600 meters, then by loosening the coupling our 
long wave length is again brought back to 1,500 meters and 
our short wave length driven still farther from the inter- 
ference at 400 meters. The desired signals will again come 
in on the long wave, but our short wave length has been 
raised to 800 meters, where it is comparatively safe from in- 
terference, as there are fewer stations using wave lengths 
of from 600 to 900 meters. 

3. Tuned as before to 1,500 and 400 meters and receiving 
from waves of 1,500 and 500 meters, we may get interference 
from waves 1,500 and 400 meters. In this case, we are in 
tune with both waves of the interference and the desired 
signals may be entirely drowned out. This may be overcome 



Crystal Detector Circuits 



295 



by simply adding inductance in the secondary or capacity in 
the primary circuit, either of which raises both our wave 
lengths to 1,600 and 500 meters. We will then get our station 
on the short wave where there is no interference. 

4. Under the same conditions as before, suppose a station 
begins sending, both waves of which are of exactly the same 
length as those of the station from which we are receiving. 
If there is no difference in the tone or intensity of the sig- 
nals, we must wait our turn, as there is no simple way of 
getting around this type of interference. However, this is, 
fortunately, a very rare case and will not often be encoun- 
tered. It may be overcome by means developed in 1918 
but not yet available for publication. 

Case 2. When in tune with the short wave length of the 
transmitting station, the types of interference are similar to 
those under Case 1, but the remedies are slightly different. 
One example will be given here, and the reader may work 
out the rest for himself. 

1. We are tuned to 1,500 and 400 meters, and are receiv- 



\/A \/ A ^Variometer 





Figs. 137, 138. — Selective Receiving Circuits. 



ing from waves of 1,600 and 400 meters. Interference of 
1,400 and 400 meters may be tuned out by adding inductance 
in the secondary circuit or capacity in the primary, either of 
which will raise our wave lengths to 1,600 and 500 meters. 
The desired signals will then come in on the 1,600 meter 
wave. 

Questions now begin to come up. How can we tell to 



296 



Experimental Wireless Stations 



which wave we are tuned? This sounds well on paper, but in 
practice how are we to determine whether we are tuned to 
the long, to the short, or to both waves? Nothing could 
be more simple. All we have to do is to add inductance to 
the primary and observe the result upon the intensity of the 
signals. If the signals are cut out altogether, we are in tune 
with the long wave, if the signals are not affected or are only 
slightly decreased in audibility, we are in tune with the 
short wave, and if they are not cut out entirely, but their 



L 



^mp 



ijHT 



i 



Fig. 139. — Loop Antenna Receiving Diagram. 



audibility is considerably diminished, we are in tune with 
both waves. 

* Is it not possible to strengthen weak signals by these 
methods? It certainly is. For instance, suppose we are re- 
ceiving from 1,500 and 500 meter waves and are tuned to 
1,500 and 400 meters. If the signals are weak, they may be 
strengthened by first increasing the inductance in the sec- 
ondary until we are tuned to 1,600 and 500 meters. The 
signals will then come in on the 500 meter waves. Then, 
by taking half as much inductance from the secondary as 
was added to it, and loosening the coupling, we .become 
tuned to 1,500 and 500 meters and are getting energy from 
both waves and consequently stronger signals." 



7. Fig. 137. Small stations will find it an advantage 
to use the series inductance in the primary circuit as 






Balancing Out Power Line Hum 297 

shown when receiving from stations using long wave 
lengths. This corresponds to the use of a loading coil 
at the transmitter. 

8. Fig. 138. Differential (Fessenden) Method. Two 
identical loose couplers connected as shown are used. 
The variometer is a form of tuner which will be described 
later, and a single slide tuner may be used instead. In 
operation the switch "a" is opened and the set is tuned 
to the desired signals. A is then closed and the vario- 
meter or single slide tuner adjusted until the signals are 
received the loudest. The condenser marked 5% must be 
adjusted so that its capacity is nearly 5 per cent more 
than the other one. The interfering impulses are not 
in tune with either half of the circuit, so that they go 
through both sides very nearly equally. As in the bridge 
method, they become neutralized and do not' affect the 
receiver. 

9. Fig. 139. Simple loop aerial connection. Elimi- 
nates natural disturbances and short interfering waves. 
When a looped aerial is used it-is used as an ordinary 
aerial for transmitting and a loop for receiving. 

10. The intermediate coupling circuit shown in Chap- 
ter XIII for the "Onde Unique" system can be used in 
the receiving station also if desired. 

BALANCING OUT POWER LINE HUM 

A method sometimes effective in eliminating power 
line disturbance is shown in Figure 140. An insulated 
wire loop of several turns is stretched for about fifty 
feet on the ground near the power line and in a manner 



298 



Experimental Wireless Stations 



which is not an obstruction. The current induced in this 
loop is opposed to the similar current picked up by the 



^^ 



V 



^E 



^Insu/crfed wire loop 
on ground near line 



Telephone « Up 
Indue tfon Coil- - """*' ""' 




B 



b 



J 



Receiving Set 
Fig. 140. — Balancing Out Disturbing Power Line Hum. 

receiving set by adjusting the coupling of A and B suit- 
ably. Ordinarily such a circuit is not needed. 

PROTECTING LOW TENSION SIGNAL CIR- 
CUITS NEAR A RADIO-TRANSMITTER 



Buzzer, telephone and similar circuits near large power 
radio transmitters are best placed in grounded metal 
conduits to avoid inductive disturbances and sometimes 



Shields 299 

special protective devices have to be used to avoid such 
troubles in unprotected lines. 

SHIELDS 

Many experiments have been made with shields to 
avoid disturbances. Antennas and coil receivers have 
been placed inside of cages which permit only electro- 
magnetic waves to pass thereto but have not been gen- 
erally found effective. Radio receiving circuits, espe- 
cially vacuum tube outfits, are often wired with insulated 
conductors which are encased in a metal braid which is 
grounded. Sometimes electron tube amplifiers are 
wholly encased in a grounded metal shielding box insu- 
lated from the circuits thereof. 



CHAPTER XX 
Special Receiving Sets 

Time Signal Receiver; Weagant's Stray Mitigator; Alexan- 
derson Barrage Receiver; Heterodyne Receiver; Action 
of Heterodyne Circuit; Phase Modified Receivers; Bal- 
ance Systems; Construction of Phase Rotator; Phase 
Shifting Explained; Multiple Unit Phase Shifting Re- 
ceivers; Uni-Control and Automatic Receivers; Capacity 
Coupling; Universal Receiving Set for Long and Short 
Damped and Undamped Wave Signals; Autodyne Re- 
ceiver; Magnetic Tube Sensitizer; Short Wave Oscil- 
lating Receiver; New Circuits. 

TIME SIGNAL FIXED SET 

It is possible to arrange a fixed adjustment set to 
receive from one certain station only, as in getting daily 
time signals. Figure 141 indicates a suitable arrange- 
ment. Coil I and II are pre-calibrated for the desired 
wave length in connection with the condenser IV and 
antenna V used. A variometer III of similar adjustment 
is provided to tune the antenna circuit to the calibrated 
receiving set so as to allow for use with antennas of 
slightly different constants due to the method of con- 
struction. A layman can be provided with such a set so 

300 






Stray Mitigator 301 

that no adjustment is necessary when the apparatus is 
once installed. Merely closing the filament lighting bat- 
tery switch permits the time signals to be read. 

WEAGANT'S STRAY MITIGATOR 

While too complicated for general use Mr. R. A. Wea- 
gant has, March 7, 1919, described a stray mitigator 
suited to long distance land station work. Three single 
turn large loops are placed in alignment and J4 wave 
length apart, and directed toward the sending station. 
The two outer loops, 1 and 2 (Figure 142), are one-half 
wave length apart and used to receive strays only be- 
cause the signals received by one loop 1 balance out 
those received by the other 2, since when the current 
induced in 2 is a maximum in the positive direction it 
is a maximum in the negative direction in I, as received 
at 4 because the signals reach 1 one-half wave length 
after they reach 2. Loops 1 and 2, however, both get 
strays, according to Weagant, at the same time, so 1 and 
2 bring strays only to 4. Weagant states that strays 
known as "grinders" come from above or below from a 
source at a distance, so all three loops, I, 2, 3, receive 
them at the same time. 

The loop 3 is placed in the middle and receives both 
strays and s ; gnals. Now then, the strays remaining from 
I and 2 are used to balance against those in 3, so that 
at 4 presumably only signals are transferred to the 
receiving set. While not eliminating all strays, remark- 
ably good results are claimed for this mitigator. The 
correct explanation is probably that since a loop receives 



302 



Experimental Wireless Stations 



only strays to which it is oriented (whether these come 
from above or sideways too) all three loops get nearly 
the same strays so that they may be eliminated by dif- 
ferential balance. The signals from I and 2 only balance 
out because those received by 3 arrive at a different time 
(out of phase) so that they will not balance against those 
received by 1 and 2. 

The Edelman Differential Wave System accomplishes 
a similar result in a different manner requiring no elabo- 



Vv 



— nnnnnnr 
1 

' '^.-Liqhtninq 
Arrester 



£*t|h 



T 



Ttf 




Fig. 141.— A Receiving Set for Time Signals. 

-3000 Meters 



Direction of 
Sending Station 




x Sfnqfe turn loop 
(Amplifier 



Signals 
R=6000meters 



j — — y* — 1_^ Signals without 

\ — V Kq) "grinder" form of stray: 



Fig. 142. — Weagant's Stray Mitigator. 



rate extensive loop systems as in Weagant's plan, and 
operates regardless of the direction from which the strays 



Barrage Receiver 



303 



come. The latter mitigator, while of more general appli- 
cation, is not yet released for publication. 

ALEXANDERSON BARRAGE RECEIVER 

Special phase rotators and bridge balanced circuits 
have been developed by E. F. W. Alexanderson and 
others so that messages can now be simultaneously trans- 
mitted and received from the same station. The strong 
sending impulses are entirely balanced out while the dis- 
tant signals are heard clearly. This is done by taking 
directly a portion of the transmitted energy and opposing 
it against the similar energy received from the local trans- 
mitter by the local receiver. This is exactly done by 
adjusting the intensity and phase correctly so that the 



dt£ 



x 



^Regular Receiver 



Fig. 143. — Heterodyne Receiving Circuit. 




received energy meets the exactly similar and opposite 
portion of the transmitted energy thus electrically ex- 
posed to it. The apparatus is not yet sufficiently simpli- 
fied for general amateur use but full information cap 



304 Experimental Wireless Stations 

be had by those interested by obtaining a copy of the 
paper read April 2, 1919, to the Institute of Radio En- 
gineers, New York. 



HETERODYNE RECEIVER 

This receiving method originated by R. Fessenden per- 
mits the tone of the received signals to be varied at will, 
thus aiding in overcoming interference, and also slightly 
increases the sensitiveness of the received signals. It 
consists (Fig. 143) essentially of an ordinary receiving 
set which is coupled with a local miniature sending set 
such as an arc or audion high frequency oscillator. If 
for example the incoming signals have a frequency of 
300,000 and the local oscillator is adjusted to a frequency 
of 300,516 the interaction sets up beats by interference 
which give a musical tone of 516 frequency in the head 
receivers. This method is particularly useful for recep- 
tion from undamped wave stations but may also be used 
with spark oscillations. 

A short wave can be converted to a long one for 
amplification at higher efficiency on this principle, the 
beats being at radio (high) frequency instead of at 
audible (low) frequency. For example a 200 meter 
wave can be converted to a 3000 meter wave in the 
local audion receiving circuits, and the latter (long) 
wave then amplified. 

HETERODYNE ACTION 

The addition of two energy waves to form beats as in 
the heterodyne or autodyne receiver is shown in Figure 



Phase Modified Receivers 



305 



144. In the autodyne the local oscillator also serves as 
a detector for the incoming oscillations slightly detuned 
therefrom so that beats result. 

It has been found that the 12,800 meter waves emitted 




1,000- Telephone Current-'' 
FlG. 144. — Principle of Heterodyne Action. 



from Nauen in Germany add with those from the station 
in South San Francisco, California, to form beats when 
the two stations happen to work simultaneously. 
PHASE MODIFIED RECEIVERS 

Much work has been done by the author and others 
on phase modified receivers for elimination and mitiga- 
tion of interference and strays. In such experiments 
either the radio frequency energy or the audio frequency 



306 Experimental Wireless Stations 

energy is slowed down by passing same through more 
or less loaded line, or by use of phase rotators as in 
Alexanderson's barrage receiver, so that any particular 
part of the wave energy can be brought in exact align- 
ment with other similar energy for complete neutraliza- 
tion or even exact addition. That is essentially all that 
the Weagant balancer does as, other explanations not- 
withstanding, it so happens that the correct phase rela- 
tions for neutralization were obtained thereby. Such 
work is not yet available for general use but soon may be. 
The phase rotators* used are merely air core induction 
regulators such as are in general use in alternating cur- 
rent power work, whereby the time occurrence of the 
received impulses can be shifted 45, 90, or up to 180 as 
required so that proper balancing can be carried out. 
The same method can be used to exclude strong inter- 
ference from one or more nearby stations, while distant 
feeble stations are still heard. Mr. Alexanderson tells 
me that he adopted the name "barrage" because of this 
ability to keep out other interfering stations. 

PHASE SHIFTING EXPLAINED 

Figure 145 shows how a portion of the effect of a 
signal wave acts when shifted against its effect on a 

* The Bellini-Tosi radio-goniometer is a phase rotator also 
and was used by Weagant in his balancing work. Two loops 
were used, one connected to one stationary coil of the 
goniometer and the other loop to the other right-angle coil. 
The usual receiving set was then connected to the third and 
movable coil of the goniometer. As the angle is changed 
between the movable and the fixed coils the phase or time 
appearance of definite portions of the radiant energy in the 
receiver is altered. 



Multiple Unit Phase 307 

nearby receiver. Enough of the local energy opposes the 
received energy from the same source at the same inten- 
sity and at the same time but in opposite polarity, so 
the result is zero. To get the opposing part to come 

T[me ^Same Wave gSame Wave 

V HOD UWilK 

A Wave ''Effect of Wave Shi f ted IdO^Ef feet of Wave Shifted 90° 

■Wave 1 



<\£C 000 

^^ Turn tA/m/oc r\nnr\ 



Result of phase shifted 
Two waves opposed wave balanced against 

Two Waves for zer0 ^sult its own effect, 

in Phase 

Fig. 145. — Illustrating Phase Tuning Methods. 



opposite at the right time it is made to travel a little 
slower (by the phase modifier) so that the effect is 
shifted i8o° to oppose the unretarded effect on the 
regular receiver. 

MULTIPLE UNIT PHASE— MODIFIED STRAY 

AND INTERFERENCE ELIMINATING 

RECEIVERS 

Highly developed multiple modified receivers remark- 
ably free from stray and interference disturbances have 
been independently developed by the author but details 
are not available for present publication. 

U. S. NAVY METHODS 

A paper by Dr. Austin, read April 7, 1920, at the 
Institute of Radio Engineers, gives some valuable data 
on U. S. Navy methods of interference mitigation. 



308 



Experimental Wireless Stations 



UNI-CONTROL RECEIVER 



A continuously variable automatic receiver, motor 
driven so as to be always at an efficient adjustment at 




c 

6 

i 



§ 

v> 

a 
£ 
o 



Capacity Coupling 



309 



300 to 3,000 meters within ten seconds' time, as described 
by Mr. R. Thompson to the Institute of Radio Engineers, 
February 5, 1919, is shown in Figure 146. 

CAPACITY COUPLING 

Fig. 147 shows a capacity coupled oscillating receiver. 




Fig. 147. — An Example of Capacity Coupling. 

UNIVERSAL RECEIVER 

• A method of receiving either damped or sustained 



• 1§ 



ft 




T 



* 



1 

2 ° 



Fig. 148. — A Circuit for Either Damped or Undamped Wave 
Reception. 



310 



Experimental Wireless Stations 



signals claimed by Weagant is shown in Figure 148. The 
coupling between 1 and 2 is merely sufficient to cause 
the circuit to act as an autodyne receiver when 4 and 2 
are detuned from the incoming sustained signals. For 
ordinary damped signals 2 and 4 are not detuned. 

RADIO FREQUENCY AMPLIFIER WITH 
CRYSTAL DETECTOR 

Figure 149 shows how a vacuum tube 1 can be used 



I- 



: t 




Crystal Defecfon^ 



L* 



^||mvw/vwv 



L3 



= Bi 



% S U * 



J 



Fig. 149. — Crystal Detector Used with Radio Frequency 
Amplifier. 

to simply amplify the incoming energy before it reaches 
the crystal or other audion detector circuit. 

AUTODYNE RECEIVER 



Figure 150 shows the use of a "tone" circuit L 2 C in 
the plate circuit to afford an "autodyne" receiver for 
reception of sustained signal energy by the beat method. 



Magnetic Tube Sensitizer 



311 



MAGNETIC TUBE SENSITIZER 

» Figure 151 shows a solenoid A wound around the 
outside of tube C and connected in series with filament 




r 



— IF- 



C": 



Fig. 150. — Autodyne Receiver. 



D to use the effect of a magnet on the electron stream B. 
This can readily be added to any tube. 

SHORT WAVE OSCILLATING RECEIVER 



A form found most useful for radio receiving at wave 
lengths in the vicinity of 200 meters when sustained short 
wave transmitters such as have been described are em- 
ployed is shown in Figure 152. The variometers are con- 
structed exactly as has been set forth in this book as is 
also the case for the condensers. Flashlight batteries 
may be soldered together in series to give the necessary 
30 volt plate battery. The circuit can be used with a 
multi-turn coil receiver instead of the antenna ground 



312 



Experimental Wireless Stations 



shown by opening the circuit at A, B, and connecting a 
coil four feet in diameter containing ioo turns No. 22 
of insulated wire thereto. 



C' 



HI 



V 



-B 



■G/ass Tube 



8> 



x 



Fig. 151. — Magnetic Tube Sensitizer. 



If the input circuit is tuned by the variometers to say 
200 meters the output or plate variometer II is adjusted 
to slightly a different wave length so that local beats will 



..'-Variometer I 



Variometer E 




Fig. 152.— A Short Wave Oscillating Receiving Circuit. 



Universal Wave Receiver 



313 






result from the incoming energy and local oscillations 
set up in the circuit. Variometer I should be moved with 
respect to variometer II to get the desired result. A 
small difference of wave length in the vicinity of 200 
meters makes a large change in the frequency. It is ac- 
cordingly possible for a large number of stations using 
audion generators or other sustained wave transmitters 
and such a receiver as this to work in the same locality 
without causing interference with one another. 

UNIVERSAL WAVE RECEIVER 

As indicated in Figure 153 it is not difficult to arrange 
a receiving set which may be used for long or short 
damped or sustained wave heterodyne reception by ap- 



■ Load Secondary 




" --Condenser Switch 



v Condenser parallel or series 



Fig. 153.— A Universal Set for Long or Short Sustained or 
Damped Wave Reception. 

plying suitable. switches. Such a set can be connected to 
AN-Gr or a multi-turn coil M, as indicated. The primary 
condenser is used in series for short, and in parallel 
for long, wave reception. 



CHAPTER XXI 
Receiving Condensers 

Construction of Fixed and Variable Condensers; Circuits for 
Condensers; Building a Condenser; Korda Air Conden- 
ser; Assembly of Plates; Geared Fine Adjustment Con- 
denser. 

The discussion which has already been given for send- 
ing condensers applies, for the most part, to receiving 
condensers. The main difference is that the insulation 
for receiving condensers does not need to be so heavy 
because of the lower potential and currents used. The 
coatings of receiving condensers are, therefore, placed 
very close together so as to secure a large capacity in a 
small space. Air is used for variable condensers to a 
large extent because it provides a convenient dielectric 
which has no hysteresis losses. On account of the low 
dielectric constant, however, other dielectric materials, 
such as castor oil, mica, paraffin paper, and glass are 
used when large capacity is desired. The capacities nec- 
essary for the receiving circuits, however, are generally 
small. The laws for parallel and series connections as 
stated for transmitting condensers apply to receiving 
condensers as well. As has already been pointed out, a 

314 



Fixed Condenser 315 

fixed and variable condenser can be used in parallel, the 
fixed condenser to approximate the desired capacity and 
the variable condenser to make up the difference. This is 
perhaps the most satisfactory and economical arrange- 
ment as large variable capacities are then unnecessary. In 
making fixed condensers, the proper capacity must be 
approximated, and can be calculated by the formulas al- 
ready given for transmitting condensers. It is well to 
make several units which may be connected in or out of 
the circuit to secure a variable step condenser. 

The proper capacity necessary for each set must be 
determined experimentally, though the approximate 
amount can be found by calculation. This is essential 
because of the variable quantities concerned, such as the 
other apparatus employed, the size of the aerial, etc., 
which is a different problem than when the transmitting 
condenser is calculated for a definite size and kind of 
transformer. The use of too little capacity can generally 
be told by the weakness of the received signal. Capacity 
should be added until the maximum sound is received. If, 
however, an excess of capacity is used, the signals will 
become indistinct. The capacity should then be lessened 
until the ragged sound disappears and is clear. 

There are many suitable 'constructions for both fixed 
and variable condensers, the designs here described being 
those most generally used. 

FIXED CONDENSER 

These are used as shunts around the detector or phones 
to- increase the intensity of the received signal. When 



316 Experimental Wireless Stations 



V 



tuning inductances having adjustable coils are used, the 
secondary or detector circuit condenser can be of the 
fixed step-by-step type. A continuously variable con- 
denser is hardly necessary except in the primary or aerial 
circuit, and since it is more expensive, particularly in the 
large sizes, the step-by-step type is best to use in parallel 
with a small balancing variable condenser as has already 
been pointed out. Aside from intensifying the received 
signals, a condenser, if of the adjustable type, permits 
fine selective tuning. 

A convenient condenser unit which may be connected 
together with duplicate units or variable capacity to se- 
cure almost any capacity is made as follows: 

CONSTRUCTION OF A RECEIVING CON- 
DENSER 

This type is suitable for a shunt circuit around con- 
tacts of small spark coils and other purposes also. 

Obtain a good grade of bond paper about .004 or .005 
(measure with a micrometer), of an inch thick and soak 
several sheets in a pot of clean melted paraffin until the 
air bubbles are driven out. When air bubbles no longer 
rise, hang the sheets up to dry and cut them into pieces 
2 inches by 3 inches. 

The coatings are made from tin foil cut to pieces I 5-8 
of an inch by 3 inches long, and smoothed out by a roller 
as described for transmitting condensers. See Figure 
45 of Chapter IX. 

Lay a strip of tin foil upon a strip of paraffined paper 
so that 3-8 of an inch of one end of the foil projects 



Construction of a Receiving Condenser 317 

beyond one of the long ends of the paper. Now lay a 
sheet of paper on top of this and again place a sheet of 
the foil, but projecting the 3-8 of an inch on the other 
end of the paper. Repeat, until the desired number of 
sheets and foil have been alternately arranged, six or 
eight sheets being a desired number. The foil should 
be arranged evenly between the paper, so that the margin 
on three sides is nearly equal. When done, the condenser 
should consist of alternate layers of foil and paper with 
every other foil projection on an opposite end of the 
paper. Now place the assembled condenser between two 
temporary boards and a clamp. Squeeze together under 
the influence of heat. This may be accomplished over a 
hot air register or open oven which is just warm enough 
to soften the paraffin of the paper sheets. Tighten up 
the clamps and remove them after the wax cools. The 
two sets of connectors are then soldered or clamped to a 
conductor of stranded copper wire, and may be mounted 
in almost any desired manner. The condenser used as a 
detector shunt may be mounted in the base of the de- 
tector stand. Switches should be provided for connect- 
ing several of these units in series, parallel, or series mul- 
tiple. About three of these units in parallel will be the 
right amount for the chopper condenser of the continuous 
wave receiving set, while a single unit will suffice for most 
of the secondary or detector circuits. Test as described 
for the transmitting condenser. The condenser should 
hold the battery charge for some little time and should 
be capable of discharging through the telephone receiver 
with an audible click several seconds after the battery- 
terminals have been disconnected from it. It is seldom 



318 Experimental Wireless Stations 

that this kind of condenser is burnt out or injured, so 
that once made, it is practically permanent. The primary 
condenser for the spark coils already described is built 
in the same manner, except that the larger dimensions 
given are used. A shunt condenser around a telegraph 
key used for sending, should have a large capacity sim- 
ilar to that used around the vibrator contacts of a coil. 
Paraffined tissue paper such as is used to wrap eatables 
and instruments may be had ready paraffined and is de- 
sirable because of the uniform thickness. The condenser 
can also be assembled by applying the foil to the paper 
while the wax is still soft and warm, making the after- 
warming and pressure unnecessary. 

KORDA AIR CONDENSER 

This type of variable condenser is in general use 
for wireless receiving sets, wave meters, and is particu- 
larly desirable in the primary or aerial circuit for tuning 
purposes. Fine adjustment is possible and when properly 
made there is little or no loss in the condenser. The 
construction is somewhat difficult, however, but since the 
plates may be had already cut and smoothed, the main 
difficulty is limited to the arrangement of the plates. It 
is not necessary to use a large number of plates provided 
the arrangement with a parallel step by step condenser 
is adopted. Such a step by step condenser should not 
have more than one or two sheets of foil and dielectric 
to each unit or step and the switch contacts used should 
be good and well cleaned. 

The plates used should be of brass or aluminum of 



Korda Air Condenser 



319 



about No. 20 B&S gauge and since the cutting is difficult 
to do by hand, they are preferably purchased already 
stamped from supply houses or else turned out in a 
lathe by a machinist. It is essential that the plates be 




k- 3 7 /¥* >J 

Fig. 154. — Variable Condenser Construction. 



perfectly flat and even. The number of plates used 
need not be more than four or six if a fixed condenser 
in parallel is also used. If the condenser is to be used 



320 Experimental Wireless Stations 

alone, from twenty-four to twelve plates should be used. 
This is for the larger or stationary plates, one less being 
used for the rotary plates. Two plates suffice for a 
vacuum tube grid condenser for short wave sets. Five 
fixed and four rotary plates make it a convenient size for 
a variable unit. 

The five fixed plates should be semi-circles 5J4 inches 
in diameter and the rotary plates of which four are 
needed should be ^ T / 2 inches in diameter, as these are 
standard sizes. It will be understod that larger units 
may be made in the same manner, using more plates. 
The several details are shown in Fig. 154. The five 
large semicircles should be placed together and three 
5-32 in. holes drilled near the edge as shown at (A). 
The four small plates are placed in the same manner, 
except that only one 5-32 inch hole is bored as shown. 

Obtain brass or copper washers 5-32 inch thick, 3-8 
of an inch in diameter and with a 5-32 inch hole at the 
center. These may be had at a supply house or hard- 
ware store. Also obtain some 5-32 inch brass rods. 

ASSEMBLING THE ROTARY PLATES 

The plates are assembled after the holes have been 
smoothed and burrs removed, by passing a piece of the 
5-32 inch rod alternately through a plate and then a 
washer. The ends of the rod should be threaded with an 
eight thirty-two die and the rod cut so that a short exten- 
sion is left beyond the plates for a handle. The plates 
are held together on the rod by two threaded washers or 
nuts l / 2 inch in diameter and 9-32 of an inch thick. The 






Assembling the Fixed Plates 321 

nuts should be turned tightly so that the plates cannot 
move after they are placed in alignment. 

ASSEMBLING THE FIXED PLATES 

A similar plan is used with the fixed plates, a rod 
being inserted in each of the three holes, and threaded 
8-32 at the ends as before, care being taken to keep the 
plates in alignment. The washers between the plates are 
placed at all three positions. A longer extension should 
be left on these rods for fastening purposes. The appear- 
ance of the assembled plates is shown at (B) of the 
figure. 

Obtain two pieces of fibre 3-16 of an inch thick and 
cut out two pieces with the shape and having holes. as 
shown at (C). The holes 1, 2, 3 correspond to the holes 
of the large plates, and the hole 4 is bored so that when 
the shaft of the movable plates is in place in it and the 
fibre is assembled on the rods, the brass washers of the 
movable plates will not touch or make contact with the 
fixed plates. This is important, as otherwise a short 
circuit would result. About y 2 inch will be sufficient ex- 
tension for this hole. The lower fibre piece is held in 
place on the rods by 8-32 nuts. It is preferably spaced a 
little distance from the lower plate by washers. The 
upper fibre piece is similarly placed after the plates have 
been located in position. 

MOUNTING 

The assembled plates must not rub or touch each 
other and must be brought into alignment, the adjustable 



322 Experimental Wireless Stations 

screw bearing at the bottom shown at (D) being a suit- 
able means. The rotary plates can be raised or lowered 
by this arrangement. The condenser may be suitably 
mounted in a box or case, and the connections, one from 
a washer on the fixed plates and one from a brass strip 
or brush bearing on the rotary shaft near the top, may 
be brought to binding posts. The excess length of the 
rods can then be cut off, and a handle provided for the 
rotary shaft. A scale and pointer can also be arranged 
on the cover, to suit. Electrose or composition knobs 
such as are used for typewriter platens (obtainable at 
supply houses) make good handles for this purpose. The 
scale may be calibrated by comparison with a known', 
standard, using a wave meter, or may be arbitrary, using 
equal divisions. A brass protractor such as is used by 
draughtsmen may be had for a few cents and makes a 
convenient scale. The pointer can be cut out of a strip 
of brass or aluminum. Two or more of these units may 
be mounted in a common case or box and switches pro- 
vided for changing the connections. Moving washers 
are preferably provided at the upper bearing to take up 
the thrust, so that the condenser may be used in any 
position.* 

MAKESHIFTS 

It is often desired to have a simple makeshift variable 
condenser for experiments. Almost any two conductors 
in any shape separated by a dielectric, so that more 

*A horizontal position for the axis is not desirable, as a 
counter-weight is necessary for balance. This type of con- 
denser can be rotated by a motor to serve in a "tikker" cir- 
cuit or indicating wave meter. 



Makeshifts 323 

or less surface may be brought into relation to form capa- 
city, are suitable. Such common things as tin cans may 
be utilized, the insulation being provided by using paper 
or even a coat of shellac or asphaltum. A can painted 
in this manner and suspended so that its height in a jar of 
salt water can be altered, connections being made to the 
can and to a plate inserted in the solution, is suitable, 
provided that every part of the exposed surface is cov- 
ered by a thin coat of the insulating varnish. Sliding 
plates similar to those described for a variable sending 
condenser may also be used. Two tin cans having dia- 
meters so that one just slides into the other after a layer 
of paper has been shellaced on the inner or sliding one 
may be used. Similar arrangements will doubtless sug- 
gest themselves to the reader and if carried out care- 
fully may serve quite well. The series capacity used in 
the aerial circuit should have a comparatively large capa- 
city. This is best obtained by using a fixed and a variable 
capacity in parallel, in which case a makeshift arrange- 
ment carefully constructed will generally have sufficient 
capacity to make it of considerable use. 

The Korda condenser described is desirable, however, 
and if immersed in a can of transformer or castor oil, 
preferably the latter, its capacity will be considerably 
increased. (See chapter on the calculation of capacity). 
The maximum capacity of such a condenser is readily cal- 
culated when the area is taken by using the formula. 

Area of a circle = 3.1416 R 2 , taking the radius R for 
the rotary plates, and dividing by 2 to find the area of the 
half circle. 



324 



Experimental Wireless Stations 



GEARED CONDENSER 

For final small adjustment so desirable in electron tube 
work an extra geared knob can be added to the usual 
condenser knob as shown in Figure 155. The author has 
improved this by using a worm gear as the adjustment. 
It is not only finer but stays fixed once it is set because 
the wheel cannot turn against the worm as is the case 
with ordinary spur wheel gears. This fine adjustment 
is important in vacuum tube and phase adjustment work. 



I 
I 
\ 



.<f 



i 



V 



^AAiwb^^ 



Fine ,*"*. 
Adjustment 



Of 



% 



\ 



% 



t 



D 



I 






j 



•I 



Panel- 



.Gears 



Condenser.-' 
Fig. 155. — A Finely Adjusted Gear Operated Condenser. 



CHAPTER XXII 
Construction of Receiving Inductances 

Tuners; Loose Couplers; Loading Coils; Sliders; Windings 
for Desired Wave Lengths; Variometer; Variometer 
Phase Rotator; Switching; Dead End Elimination; Tens 
and Units Connection; Multilayer Coils; Compact Long 
Wave Length Coils; Couplers for Long Wave Lengths; 
Dimensions for Various Wave Lengths; Plural Receiv- 
ing Sets. 

Whatever type of tuning is adopted, the inductances 
used should be carefully constructed with accurate and 
delicate adjustments. Every part should be nicely made 
and great care taken with the insulation and contacts. 
The cores and ends used are preferably made from hard 
rubber, fibre or molded composition, but wood and paper 
when dry and carefully shellaced may be substituted. The 
wire used should be uniform, and may either be bare or 
insulated. Bare wire is spaced by means of a thread or 
a groove cut into the core, while insulated wire is sep- 
arated naturally. Contact is best made when bare wire 
is used. Enameled wire is neat and useful since a con- 
tact portion is readily scraped from the wire. Cotton and 

325 



326 Experimental Wireless Stations 

silk insulations are difficult to scrape for contact with 
sliders, so that the job is neat and effective. The only 
objection to enameled wire seems to be that the turns 
are brought too close together, so that an undesirable 
electrostatic capacity is formed between the adjacent 
turns. Wood may be used for bases. All metallic parts 
including connecting wires should be carefully insulated 
from each other and even from wood, by using hard 
rubber sheeting and tubes. In receiving delicate and 
minute oscillations from distance stations, every detail 
counts for efficiency and too much care cannot be taken 
if the maximum results are desired. Holes are prefer- 
ably filled up with tar or wax, and shields provided to 
prevent injury or leakage to or from the wires. In the 
following designs, descriptions will be given for induct- 
ances of standard design and merit. While there are 
varied forms for the detailed constructions, and much 
ingenuity can be exercised, the main dimensions and de- 
sign should generally be adhered to, to secure efficient 
instruments. It should be remembered that a coil com- 
prises principally inductance but also has some capacity. 
The windings are usually designed to reduce this capacity 
in the coil to as negligible a value as is possible. An 
example is the honeycomb or yarn warp wound coil. 

TUNERS, SLIDE TYPE 

This form is commonly employed for tuning, bridge, 
loading, and similar methods as has already been de- 
scribed. While only one slider is described, it will be 
understood that duplicate sliders can be provided on 



Tuners, Slide Type 



327 



other parts of the circumference of the core and wire. 
It is well to provide binding posts for the wire terminals 
in every case so that a variety of utility is the result. 
(See Fig. 156.) 

Core. This may be turned out from hard wood, but 
since wood shrinks, a rubber, fibre, composition, or even 
a shellaced paper tube is much preferred. Suitable tubes 
may be had from supply houses. Paper or fibre tubes 
can be made by rolling up and gluing a sheet of the thin 



>/iden. 




.■-Binding., 

i /Urn 



7 \ 



Hole -for Screw 



Post—* 



3 a 



"-Knob 
-Hole for Rod 



H0le "'"' S S pr?nJ"*$ r/e* 
Metal Tip/ 

Figs. 156, 157. — Tuner Construction. 



fibre into the desired size. Hollow tubes have the addi- 
tional advantage of light weight. The diameter of the 
tube may be any convenient size between 2^ inches and 
6 inches, the smaller diameters providing sharper ad- 
justment. 3*^ inches is a desirable diameter. If bare 
wire is to be used on the fibre, rubber or composition 
tube, it is very desirable to turn or have a machinist 
turn a thread on the core. About 18 threads to the inch 
makes a suitable thread for use with No. 22 wire, which 



328 Experimental Wireless Stations 

is a common size in favor. The threads can be cut to 
within y 2 inch or so from each end. The length of the 
tube used may be from 3 inches to 12 inches or more as 
desired. 

The winding. Use soft copper wire of not more than 
No. 24 in fineness, nor less than No. 18 in coarseness, 
No. 20 or 22 being preferred. The winding can be done 
by hand if care is taken, but a lathe or makeshift lathe 
is best to use. The wire should be wound tightly and 
evenly, avoiding kinks. When the core is threaded, this 
is easy. If bare wire is used without threading the core, 
the turns should be spaced by winding the wire with a 
turn of heavy linen thread, so that each turn is spaced 
by the thickness of the thread and the adjacent turns of 
wire do not touch each other. Enameled wire is wound 
without spacing. Cotton or silk insulation is not recom- 
mended for wire for tuners of this type. The bare wire 
is preferred. Then ends of the wire can be fastened by 
means of a small hole drilled at the end of the core or else 
by means of a small screw. If hard drawn copper wire, 
such as may be had at hardware stores, is available, it is 
preferred as it is more durable and easier to wind. 

CORE ENDS— BASE 

While the core ends must be of a size corresponding to 
the diameter of the tube used, which may vary from 2 in. 
to 6 in., a margin should be provided to allow for clear- 
ance from a base, sliders, and so on. The ends are pref- 
erably square and may be easily fastened to the cores in 
any desired manner. For solid wood cores, wood screws 



Sliders 329 

may be used. Tubings are best fastened by turning a 
recess in the inner end of the core end which will fit over 
the tube snugly. Another method is to provide plug 
ends for the tube, which are then screwed on the core 
ends. When assembled, the tuner should set true. The 
use of a base is optional and is hardly necessary except 
for appearance and possibly convenience. The binding 
posts can be brought out on the core ends. 



SLIDERS 

(See Fig. 157.) These may be any suitable type which 
will make a step by step contact with the several turns 
of wire without undue friction. The slider rods are 
preferably of square or rectangular shape, as round rods 
must be used doubly to prevent undesired turning. The 
rod is cut as long as the length of the core plus the thick- 
ness of the core ends, which should not be over £4 inch, 
plus a little extra for connections or a binding post. While 
only one form of slider is shown, to avoid unnecessary 
duplication, it will be understood that many other forms 
may be used. The essential feature of sliders is that 
they should make good contact with only one turn of wire 
at a time and without too much friction. If the slider 
touches two turns at once (which will happen if care is 
not taken), the turn is short circuited. This is not de- 
sirable as the intensity of the received signals is thus 
lessened. The spiral spring shown can be coiled from 
No. 22 spring brass, and a round piece of copper wire 
smoothed off to a round surface is soldered on the tip. 



330 Experimental Wireless Stations 

The length of the spiral should be enough to make contact 
with the wire after the slider is in place. A roller con- 
tact may also be used. While connection with the slider 
can be made through the rod by the sliding contact 
which results, this method is not desirable and a flexible 
insulated wire is best soldered directly to the slider. The 
knob is for convenience in handling, and can be made 
from hard rubber or purchased already molded. Sliders 
and rods may be had in the open market. The slider 
should slide on the rod without sticking. Loading coils 
may be made without sliders, by taking taps off from 
every ten or twenty turns and using multi-point switches. 
The wire when wound on smooth forms should be coated 
with two coats of shellac and allowed to dry. The por- 
tion for contact is then scraped clean for a distance along 
the length of the coil and under the slider, of about Yz 
inch. This may be accomplished by using a knife or a 
small block of wood covered with emery cloth. The 
wire should be scraped until it shows clean and bright. 
Two wooden strips may be temporarily fastened on the 
core the d^esired distance apart to serve as a guide so 
that the scraped portion will be of uniform width. If 
several sliders are used, two may be taken from the top 
or one from each side, or all, as desired. The use of 
bare wire wound in a threaded tube core is best adopted 
for a standard, the diameter being 3 inches and length 
10 inches, as this will give a serviceable instrument with 
a wide range of utility. Wires. wound on smooth cores 
or wood cores, particularly enamelled wire, tend to loosen 
after a time, in which case it is best to either rewind the 
coil or make a new one. 






Variometers 



331 



VARIOMETER 

A variometer is a form of tuner without any sliding 
or variable contacts and depends solely on the variable 
coupling between its two parts which are connected to- 



Terminals 



Knok 




'■Wire 
-Variometer Construction. 



gether. It is quite easily made and is very useful in 
connection with other apparatus, particularly as a loading 
coil. It may be used alone for short wave lengths. 

VARIOMETER AS A PHASE ROTATOR 

Phase modification experiments at radio frequency can be 
made by inserting a special variometer in series with the 
primary circuit of any radio receiver. Keep the terminals of 
the two coils separate and bring them out to extra binding 
posts. Add a third coil constructed like the stationary coil 
but placed at right angles thereto. Connect one circuit to 
be balanced to one stationary coil and the other circuit to 
be balanced against the first, to the other stationary coil. 
Connect the usual radio receiver to the movable coil. By 
adjusting the phase and separately adjusting the intensity 
of coupling some remarkable results are open to the ad- 
vanced experimenter. See the 1919 and 1920 proceedings of 
the Institute of Engineers for details of some of such ex- 
periments. 



332 Experimental Wireless Stations 

A suitable construction is indicated in Fig. 158. The 
cores are of hollow fibre, rubber, composition or paper 
and may be made as has already been described. The 
stationary core is 6 in. in diameter and 21-8 inches wide. 
The inner and movable core is 4 7-8 inches in diameter 
and 21-8 inches wide. The larger core is wound with 
about forty feet of No. 22 insulated wire, so that a space 
of y 2 inch is left at the center. This will make about 24 
turns on each side of the space. The small core is wound 
in the same way, except that 28 turns are wound on each 
side of the space. Both parts of each core should have 
the same number of turns. 

One-quarter inch holes are now bored or punched, at 
opposite points of the two cores, in the center of the y 2 
inch bare band, for a rod. This rod is a piece of J4 mcn 
round brass yy 2 inches long, and is passed through the 
holes as shown in the figure. Now take a piece of No. 18 
bare wire about $y 2 inches long and fasten it as shown, 
soldering it at the center to the 34 mcn r °d and bringing 
the ends through the small core. This is to make the 
inner coil fast to the rod so that it may be rotated. Rub- 
ber or fibre washers (W) should be placed as shown, so 
that the inner coil is free to rotate within the outer coil. 
The two coils are connected together as shown with a 
short length of flexible insulated wire. Additional layers 
of wire may be added for use with longer wave length 
circuits. 

Mounting. This may be carried out as desired, a box 
6y 2 inches cube being suitable. Binding posts should be 
provided and connections made so that starting with the 
end of one coil, the wire continues until the opposite end 



Loose Coupler 333 

of the other coil is reached at the other binding post. 
A knob with a pointer and a scale may be provided as 
described for the variable condenser of Chapter XVIII. 
Use like a tuning- or unloading coil. About 75 feet of the 
wire will be needed. The coils may be shellaced and the 
instrument finished as desired. In mounting the instru- 
ment, the outer coil is fastened rigidly to the case of 
cover so that only the inner coil is rotable. When at 
right angles the two coils are neutral, while when con- 
centric the closest coupling adjustment is reached. The 
inductance will be nearly uniformly variable as it has 
almost a straight line curve. 

LOOSE COUPLER 

The loose coupler is in general favor at the present 
time. With it and condensers, a wide variety of tuning 
and coupling is possible. The set can be tuned to either 
the long or short waves or both and when the maximum 
point is found the interfering stations can often be tuned 
out by making the coupling very small. (That is, pull- 
ing the primary far away from the secondary or vice 
versa.) The following design and data is for one of 
these instruments and two will be required if the Fessen- 
den differential method is employed. (See Fig. 159.) 



PRIMARY 



long. The wall should not be more than 1-8 inch thick. 



334 



Experimental Wireless Stations 



B&S gauge bare or enameled wire, preferably the for- 
mer, in threaded grooves. Start winding 9-16 of an inch 
from one end and wind until within 9-16 of the other end. 
Heads for Primary. J / 2 in. thick, 4x4^ in., smoothed 
on all sides. Find the center of each piece (two needed). 
These pieces are now centered in a chuck in a lathe so 
that the lathe center is Y^ inch below the marked center of 
the pieces. One piece is made with a hole 3 inches in 




Bridge. 1 
: '^W////M'' Hoks ^r Rods 



Primary Head 
Inside 



'--■Notched Poini(Enlarged) 



2£ 



Rod*' b 1 

^Spring Loop' 
Fig. 159. — Loose Coupler Construction. 



•Tubes- 



diameter through it, while the other piece is bored, with 
this same size, to have a depth of only 3-8 of an inch. 
When done, one piece will have a hole 3 inches in dia- 
meter through it while the other will have a smaller hole 
coming within 1-8 inch of the outer surface. 



Base. Three-fourths of an inch thick, 6 inches wide 



Loose Coupler 335 

and 16 inches long. (Hardwood.) Mount the primary 
at one end so that it sets true and is nicely spaced, using 
screws driven from the bottom of the base into the heads, 
the screws being countersunk. A single slider may now 
be provided, as shown and as has been described for 
tuners. It is understood that the primary core with the 
winding, is mounted in the heads, using cement, so that 
the core and wire are held in the openings in the heads 
and so that the head with the hole all the way through 
it faces toward the long end of the base. (See figure.) 

SECONDARY 

Core. Hardwood cylinder turned from dry wood.* 
Diameter, 2 J / 2 inches. Length, 5 inches. (See Fig. 159.) 
Have a machinist mill a slot 3-16 wide by 3-8 deep as 
shown at (a) the whole length of the core. This should 
be smooth when done. Inasmuch as bare wire is to be 
used, it would be well to have threads turned on the 
cylinder before the milling is done. These should be 20 
to the inch, and very light. Wind with No. 26 B&S hard 
drawn copper wire. Threads may be used, spacing the 
turns with linen thread, if the machine threads cannot 
be cut. Use considerable pressure in winding, as the con- 
tact is to be made from below. The linen thread used 
should be about as thick as the wire used. Start ^ m ch 
from one end and wind to }i inch of the other. 

* A hollow tube may be used if a frame is provided for 
the slot. Instead of using this slot with a slider it is satis- 
factory to bring the turns out in groups of tens and units 
to two switches which may be mounted on the movable 
head. 



336 Experimental Wireless Stations 

Head. One needed. %. inch stock, cut 3^4 inches 
square with a hole bored in center to a depth of y% of 
an inch. This hole is 2 y 2 inches in diameter and is turned 
as before. 

Attach the head to the secondary core at the }i in. end 
by small screws started from the back of the head and 
screwed into the core. The secondary slider is made so 
that more or less wire is included in the circuit when the 
rod ( See b) is moved in or out, and allows of adjust- 
ment after the secondary is within the primary coil. This 
slider is made from a piece of 5-32 inch brass rod, 7 
inches long, to one end of which a small loop of thin 
spring brass 5-32 inch wide, is soldered, as shown. A 
rounded point is then soldered on the upper part of this 
spring to make contact with a single turn of wire at a 
time. Note the notch. This is made by a few strokes 
with a fine three-cornered file. A handle is provided at 
the other end of the rod. The slider is mounted in 
the milled slot and extends through the head through a 
small hole. 

MOUNTINGS 

The mountings are shown clearly in the figure. Bind- 
ing posts should be provided and flexible insulated wires 
should be brought to the slider rods. The inner end of 
the secondary coil can be brought to the back by either 
boring a hole through the cylinder or else making a 
groove in one side of the milled slot so that the wire im- 
bedded in it cannot possibly make contact with the slider. 
The ends of both primary and secondary should be 






Mountings 337 

brought out to binding posts. The two pieces of tubing 
which act as bearings to support the secondary have an 
internal diameter of Y^ inch and are 1J/2 inches long. 
They are forced into holes drilled in the secondary head. 
The rods on which the secondary slides are 10^2 inches 
long and are supported as shown, one end being fastened 
by passing through holes in the inner head of the primary 
and the other end being fastened to a small bridge fas- 
tened to the base. The latter is 1x1x4 inches long. Small 
nuts serve to hold the rods in place. The coils should 
be mounted so that the secondary will slide freely into 
the primary. The remainder of the instrument is left 
to the individual worker and presents no difficulty. Pro- 
vided that the general dimensions are preserved, any 
suitable mounting may be used. In using two of these 
with a Fessenden interference preventing circuit, the con- 
denser marked 5 per cent must be calibrated so that it 
is about 5 per cent different in capacity than the other 
one. This may be accomplished by arranging the scale 
on this capacity so that when the pointer is on zero, the 
condenser will really be in mesh to approximately 5 per 
cent. 

A receiving loose coupler can be made on the pancake 
plan using two flat spirals of wire, one of which is ad- 
justable with respect to the other, as for the transmitting 
oscillation transformer. The spacing, however, is ac- 
complished by using a thin insulated wire strip such as is 
used for transformer coils, and the turns can be close 
together on account of the low potentials used. Such an 
arrangement has very little if any advantage over the 
loose coupler described, particularly if a variometer is 



338 



Experimental. Wireless Stations 



also used, so the duplicated description will be omitted. 
The method of using the apparatus described has already 
been fully set forth. 

The reader with limited tools can, of course, make a 
simpler arrangement. It is possible to make tuning in- 
struments with little or no facilities and tools. 

Fig. 1 60 shows another suitable manner of mounting 
the loose coupler in a box or on a panel. The tops of the 



w/////////////////////////////////zm 



w 




Fig. 160. — Mounting for Receiving Inductances. 



e. 



Receiving Apparatus-' 
10 turns each Single turns 




SwitchXS 



Secondary 



Switch — 



Fig. 161.— Method of Tens and Unit Switching. 






windings are brought to the switches by means of a flex- 
ible cable. Units and tens are used so that nice adjust- 
ment is possible. Many prefer this type. 



Multi-Layer Coils 



339 



MULTI-LAYER COILS 

For portable use coils for long wave length circuits 
can best be of the banked turn type shown in Figure 
162 One turn is wound successively in each of the lay- 
ers from one end to the other in the order shown by the 




Fig. 162. — Method of Winding Banked Turn Multi-Layer Coils. 

numbers. This reduces the capacity of the winding. 
Figure 163 shows how a coil of small bulk may be wound 
for both the primary and secondary of a loose coupler 
for long wave lengths. For 16,000 meters maximum with 




Fig. 163.— A Long Wave Length Coil Wound in Small Space. 



340 Experimental Wireless Stations 

a variable air condenser having eleven movable plates 
of four inch diameter the coil may consist of a fibre core 
2.y 2 inches inside diameter, 3^ inches outside diameter, 
and 5-16 inch wide wound full with number 31 S. S. C. 
wire with taps taken at 50, 20, 10, 5, 5, 5, 3, 2 per cent 
respectively of the total turns. While less efficient, long 
distance signals can be heard with such a coil. 

LONG WAVE LENGTH STATIONS 

There are only a few stations of very long wave length 
now in operation and a number of these are of the 
undamped wave type. Wave lengths of 6,000 to 16,000 
meters may be employed, though 14,000 meters is the 
most recent limit for long distance work. It was con- 
sidered quite a feat for an amateur to hear such stations. 
This may be easily done, however, either by constructing 
a long receiving aerial or by loading an ordinary multi- 
turn coil or aerial with inductance. A suitable long wave 
receiving aerial may consist of a single No. 14 wire sup- 
ported about thirty feet from the ground and 1,000, 
3,000 or even 5,000 feet long, preferably running in a 
straight line and insulated at the supports. Another 
method which may work if conditions are right is to sim- 
ply connect the aerial terminal of the receiving set to 
one binding post of a small variable condenser, the other 
binding post of which is connected to one of the wires of 
a telephone line. When this is done no telephone con- 
versation can be heard, but the telephone system is used 
as an aerial and brought to a suitable wave length by 
means of the series variable condenser. All" the other 
connections and tuning are the same as usual. 






Loose Couplers for Long Wave Lengths 341 

LOOSE COUPLERS FOR LONG WAVE 
LENGTHS 

Tuners for long wave lengths simply are made larger 
with more turns of wire and should be constructed with 
taps at intervals so that adjustments may be made. To 
say that a certain tuner has a certain wave length is 
misleading, as wave length depends upon the product of 
capacity and inductance as pointed out in the text where- 
as the tuner itself is only used to supply a portion of the 
inductance. 

The accompanying table gives data which will serve 
as a guide in constructing loose couplers of correct 
dimensions. These were calculated by taking the aver- 
age capacity of a large number of aerials from the small- 
est to the largest into account. The variable condenser to 
be used in the secondary circuit should have a maximum 
capacity of about .0009 Mfds. if a crystal detector is to 
be used and about one-third of this if an audion detector 
is to be employed. In practice only about three-tenths 
of the condenser capacity may be needed. More turns 
are used for the secondary in the case of audion detec- 
tors because they are potentially operated devices of 
high resistance and work best with large secondary in- 
ductance and small capacity. In any case it is desir- 
able to add to the wave length by means of series induc- 
tance rather than shunt capacity as Dr. Austin has found 
that the efficiency is decreased by the parallel condenser. 
When considerable inductance is added in this manner 
the circuit is said to be "stiffened" and this is supposed 
to slightly reduce trouble from static. 



342 Experimental Wireless Stations 

Loading coils for long wave lengths coils may be con- 
structed in the same way as the primary coils given in 
the table. In loading a small aerial to a long wave 
length both the primary and secondary circuits should 
be loaded as the ordinary secondary of the receiving 
loose coupler alone is not large enough. The loading 
coils in the two circuits may be coupled together like 
loose couplers or separated like straight tuners. The 
large cores may be made by wrapping many layers of 
paraffined paper around a cylinder and removing this 
tube when cold. 

Wave lengths less than the maximum capacity may 
be had by taking out taps at intervals to a switch. 

TABLE FOR LOOSE COUPLERS AND LOAD- 
ING COILS 

WAVE LENGTH 3,000 METERS 

Primary: core 4^" long by 4" diameter, tightly 
wound with a single full layer of No. 26 S. S. C. wire. 

Secondary: core 3^" diameter by 4" long, wound 
tightly with a single layer of No. 28 S. C. C. wire for 
use with crystal detector or with No. 34 for use with 
audion. See Figure 164. 

WAVE LENGTH 6,000 METERS 

Primary : core 8" long by 5" diameter wound with sin- 
gle layer of No. 24 S. C. C. wire. 

Secondary : core 7>4" long by 4^" diameter,' wound 



i 



Coils for Long Wave Lengths 



343 



with a single layer of No. 30 S. C. C. wire for use with 
crystal detector or with No. 34 wire for use with audion. 

WAVE LENGTH 14,000 METERS 

Primary : core 7^" diameter by 12" long wound tightly 
with single layer of No. 24 S. C. C. wire. 

Secondary : core 11^" long by 7" diameter wound with 
single tight layer of No. 30 S. C. C. wire for crystal 
detector use or with No. 34 wire for audion circuit. 



/V/'/rwry 


I 


< 


Lenaih > 


Y 




Fig. 164. — A Receiving Transformer for Long Wave Lengths. 

With small aerials an additional primary loading coil 
of similar dimensions may be required in series with the 
primary coil. An aerial intended for only 200 meters has 
been successfully loaded to 8,000 meters and has received 
signals over 4,000 miles with the aid of an amplifying 
audion detector. 

DEAD ENDS 



The unused portion of a tuning coil or cover is said to 
be "dead" and may absorb some energy thus reducing the 
efficiency. This is almost eliminated by switching ar- 
rangements which entirely cut out the unused turns. 



344 



Experimental Wireless Stations 



The principle is shown in Figure 165 which shows dia- 
grammatically a form of switch constructed by the 
author for this purpose. Only the primary is here shown 
as the secondary winding may be arranged in the same 
way. 

A wide range of wave lengths is thus possible in a 
single receiving set. The coil is divided into a number 
of insulating series of turns O, O, etc., which are con- 
nected to a switch built like a commutator so that con- 
tacts P, P, P, etc., may successively cause additional 




w 



xi m_ 



Fig. 165.— A Dead End Switch. 



turns to be included in the circuit while at the same time 
unused turns at the other end of the coil are open cir- 
cuited so that they cannot absorb the energy. Contact 
with the ground is made through slip ring Q which 
rotates with the switch. Each contact P, P, is of course 
insulated from the others and all are placed at equal 
intervals. 



Plural Keceiving Sets 345 

PLURAL RECEIVING SETS 

Another plan is to make a number of separate and 
independent receiving sets or couplers, each exactly right 
to receive at a certain wave length or from a certain 
station. A switch is then made to put the desired set 
in and the others are not in use at such time. 



CHAPTER XXIII 
Making the Wireless Set Work 

Trouble Finding; Principle Faults Found; How to Make 
Repairs; Reasons for Various Failures; Improving Poor 
Signals. 

WHEN THE WIRELESS SET REFUSES TO 
WORK 

Probably a majority of the difficulties arise from a 
misconception or ignorance of the fundamental prin- 
ciples involved; for example, (i) the use of a single 
wire for a lead-in from an aerial composed of six such 
wires, (2) the use of too small or too large a condenser 
for the transmitting circuit, (3) faulty insulation or 
design of instrument, such as using a helix or oscillation 
transformer for a y 2 kilowatt set which has No. 14 wire 
for its primary. 

"I get a good spark, but cannot radiate any energy." 
Probably causes are a broken conductor in the aerial 
circuit, an overheated gap, too short or too long a gap, 
poor or practically no ground connection, enormous 
resistance due to loose contact, a broken wire, dry earth 
connection, a broken condenser plate, punctured insula- 

346 



When the Wireless Set Refuses to Work 347 

tion, too much or too little primary or secondary induc- 
tance or both, causing a lack of resonance, a broken 
aerial insulator, grounded lead-in wire, coupling too loose, 
or again, the values of capacity, inductance, frequency, 
voltage or resistance may be such as to prevent free 
radiation. Occasionally an aerial will really radiate, the 
apparent failure being due to a burned out hot wire am- 
meter, which is used as an indicator. The proper relation 
of the values for capacity, inductance, resistance, voltage, 
amperage, frequency, and the coupling used are funda- 
mental and any variation will cause some degree of loss 
or failure. Total failure is generally due to a definite 
leakage caused by a breakdown in the circuits. 

"I am using one kilowatt of power, but cannot reach 
a friend fifteen miles away." The cause may be one 
already given, but in a case in mind the difficulty was 
due to the use of too small an aerial, a poor ground and 
very poor tuning. 

"I cannot get a good spark discharge." This is often 
due to the use of too small electrodes, too much power 
for the size of the gap, lack of cooling, too short a gap, 
a leaking or broken condenser; or again, it may be due 
to the use of long connecting wires of small cross sec- 
tion, such as were found in one particular case where the 
connecting wires were heated hot. 

"I cannot get my set down to 200 meters and radiate 
enough energy to affect my hot wire meter." A variety 
of causes may include the use of too large a condenser, 
an inductance consisting of a coil of too great diameter, 
a poor design of oscillation transformer, too long wires 
for connections, loose contacts of the clips, or connect- 



348 Experimental Wireless Stations 

ing wires of too small a cross section. In many eases, 
an inductance coil of the cylinder type will give better 
results with a smaller diameter, say six inches or less, 
and a large conductor, say No. o to 4, than is ordinarily 
used. The aim should be to use a condenser and induc- 
tance which will allow at least one complete turn of the 
inductance to be included in the primary 200 meter cir- 
cuit. A pancake type of oscillation transformer embody- 
ing this principle of small diameter and large conducting 
surface is also suitable. 

"I can hear NAX clearly, why cannot I get Arling- 
ton?" The usual reason for this is that a small station 
has insufficient wire in use to attain the necessary high 
wave length. It is a simple matter to construct a large 
loading coil, with taps, to bring a small set up to the 
longest wave length now in general use. 

"A station 150 miles from here formerly came in very 
strong, but now I can hardly hear it." It was found that 
the station mentioned had changed its wave length, but 
the cause might have been poor contact of the sliders 
or coupler switches or a non-sensitive detector. Often, 
after some months, a conductor used in the circuits will 
become grounded or broken. 

"My set tests out fine with a buzzer, but I cannot get 
even static." This failure is due to a poor ground or no 
ground, or a grounded aerial, or a broken lead-in, or 
a broken wire in the primary inductance (usually near 
the binding posts), or it may be merely a case requiring 
intelligent tuning. 

"I am operating a ship station using a motor generator 
set, but I have to connect a battery across the fields to 



When the Wireless Set Refuses to Work 349 

get the generator started." This often happens with 
small generators because of a loss of magnetism due to 
a variety of causes, such as faulty connection, the iron 
used in construction, etc. A few dry cells are generally 
sufficient to supply the starting energizing current, after 
which the fields build up rapidly. 

"My audion is noisy." The "B" battery has become 
leaky and polarized. Often dry batteries deteriorate so 
that they give a fluctuating current. 






CHAPTER XXIV 
Miscellaneous Applications 

Railroad Wireless; Forest Fire Prevention; Automobile 
Wireless; Aeroplane Sets; Wireless Compass; Bellini 
Tosi Apparatus; Multiple and Ground Aerials; Balancing 
Aerials ; Telemechanics. 

RAILROAD WIRELESS 



Railroad wireless telegraphy and telephony differs in 
no way from radiocommunication for other purposes 
except that the aerial consists of two or three wires sus- 
pended just a little above the train car while the ground 
is through the trucks to the rails. Couplings are provided 
for the aerial between cars. The Delaware and Lacka- 
wanna Railroad has had experimental success with such 
moving stations in conjunction with a few fixed Ian 
stations. Communication has been regularly establishe 
with the moving trains both ways, even when the trai 
is passing through a tunnel. 



h 



FOREST FIRE PREVENTION 



Radio apparatus is valuable as an aid in prompt reports 
on forest fires before conflagration can start. The author 

350 






Automobile Wireless 351 

was a pioneer in this beneficial application now adopted 
by several governments. 



AUTOMOBILE WIRELESS 

Successful communication may be established over 
several miles with a small wireless station on an auto- 
mobile, using a small aerial suspended a few feet above 
or within the top and using the metal body of the car 
as a counterbalance in lieu of a ground. For army use, 
the automobile is merely used to transport and contain 
the apparatus and a portable aerial is rapidly erected 
when communication is to be established. A multi-turn 
coil receiver as described in Chapter III may be carried 
complete in an automobile. 

AEROPLANE WIRELESS 

Wireless communication is successfully used on aero- 
planes to communicate to military bases from the air or 
enemy territory. The apparatus comprises a small sending 
and receiving station of light weight. Remarkable suc- 
cess has been attained over long ranges with radio tele- 
phone, telegraph, and direction finding equipment. The 
receivers are provided with sound protectors, but receiv- 
ing is less successful than sending because of the propellor 
noise. This defect has been overcome to an extent by 
using sound insulated telephone head pieces. The aerial 
is generally mounted on the planes and a counterpoise 
or additional aerial is used instead of a ground. Hanging 
aerials from reels, etc., though used in the recent war, 
are considered dangerous and obsolete. The total weight 



352 Experimental Wireless Stations 

of the equipment need not be over 50 pounds. Use of 
the wireless to direct gun fire and report troop move- 
ments has been very successful. The U. S. planes in 
France, except chasers, could be maneuvered via radio- 
telephone. They carried vacuum tube sets. 

WIRELESS COMPASS 

The Bellini and Tosi compass, of which a few are in 
use, utilizes an almost closed triangular oscillating an- 
tenna which radiates and also receives the strongest in 
its own plane and the least at right angles thereto. Two 
partially closed looped aerials are placed at right angles 
to each other and each is connected to a primary of a 
loose coupler having two primaries at right angles to 
each other and a single secondary winding which is 
rotatable therein. For any position of this secondary 
winding the received energy will be proportionately due 
to the two primaries so that by observing when the 
received signals are strongest the sending station can 
be located within two or three degrees. This is most 
useful in foggy weather. For sending the same arrange- 
ment is used with a transmitting oscillator connected to 
the two aerials in the same manner so that signals can 
be sent out strongest in a desired direction. International 
radio regulations require such stations to use small powe 
and low wave lengths, this being necessary in order t 
avoid interference with other communications. This 
system has been largely replaced by the multi-turn coil 
receiver. A refinement of the latter is now used by the 
U. S. Navy, 



11 

; 



Wireless Compass 



353 



The set uses no ground connection and is shown in 
Figure 166. The aerials A, B, respectively are connected 
to the primaries A', B' respectively of a loose coupler 
called a goniometer. The secondary S, wound on a 
spherical core connects to an ordinary detector circuit 
and is movable by means of handle R which carries a 

'"Spar 



Bellini- Tosi 
Direction Finder 




Fig. 166.— Bellini-Tosi Direction Finder. 



pointer so that degrees may be read on a scale O. In 
practice a slightly elaborated arrangement is used. For 
purposes of demonstration it is not difficult to rig up an 
outfit of this kind. 



354 Experimental Wireless Stations 

With the Telefunken compass (now obsolete in the 
U. S. A.) an ordinary antenna on a ship may be used 
in conjunction with shore stations. Thirty-two separate 
aerials arranged in the form of an umbrella are used at 
the shore station for sending, a rotatable switch being 
provided so that each antenna may be separately and 
successively connected to the sending apparatus. Aboard 
the ship the direction is determined by comparing signal 
strengths. Various other arrangements have also been 
proposed. The multi-turn coil has proven successful on 
aeroplanes as a radio compass. 

MULTIPLE TUNED ANTENNA 

The radiation resistance of a large antenna is an im- 
portant item. This has been reduced by a recent method 
called the multiple tuned antenna principle. The trans- 
mitting antenna is simply grounded at a number of 
points along its length, via tuning coil inductances. The 
arrangement for a large Trans-Atlantic station is de- 
scribed in a paper by E. Alexanderson, read at the Oc- 
tober i, 1919, meeting of the American Institute of Elec- 
trical Engineers. 

LOW GROUND AERIALS 



Experiments with grounded aerials show that sig- 
nals may be received for distances of at least 3,000 miles 
with an ordinary receiving set by simply using a bare 
or insulated wire spread upon or supported a few feet 
either above or below the ground as an aerial with a 






Balancing Aerials 355 

counterpoise. A single wire has been found to be the 
best especially if a Y is connected to its ends and such 
an antenna has also been found to be directive. The 
counterpoise is best made exactly like the aerial and ar- 
ranged opposite it so that the receiving set is at the 
middle of a symmetrically placed conductor adjacent to 
the ground. For sending purposes such an arrangement 
has not been found effective except over a short distance. 

BALANCING AERIALS 

The Marconi duplex stations were designed to use a 
balancing aerial at the receiving station to overcome inter- 
ference from the sending end of the station a number of 
miles away which is in simultaneous use. This is simply 
an aerial placed at right angles to the receiving aerial 
and of lesser height which is coupled to the main aerial 
through a loose coupler in such a way that the energy 
received by the one aerial is neutralized by that received 
by the other from the strong nearby station. The large 
aerial receives the long distance signals as usual but the 
balancing aerial being both lower and at right angles 
does not receive enough energy from the distant station 
to deter the reception of signals therefrom. A single 
horizontal wire suffices for the balancing aerial. This 
method has been superseded. 

TELEMECHANICS 

Wireless controlled torpedoes, boats, fog guns, etc., 
have b^en successfully experimented with so that ap- 



356 Experimental Wireless Stations 

plications may be expected to come into use soon. Most 
of this work has been done with the use of a coheror 
receptor and various mechanical switch and tuning ar- 
rangements. It is now possible, however, to use the 
more sensitive audion and amplified circuits already 
mentioned for this purpose. A simply made outfit for 
demonstrating the various possible applications is de- 
scribed in Chapter XIII of the book "Experiments" by 
the author which may be obtained for $1.50. 

Telemechanics is now a practical art. Large boats are 
exactly controllable by radio for naval purposes. Com- 
pressed air mechanisms governed by electrically oper- 
ated valves included in audion amplifier and relay cir- 
cuits with proper selection permit successful control. 
Details are not released for publication yet. 



CHAPTER XXV 
Time and Weather Signals 

How Signals Are Transmitted and How to Receive Them; 
Naval Stations Sending Information; Codes Used; Ex- 
ample of Deciphered Code. 

TRANSMISSION OF TIME SIGNALS BY 
NAVAL RADIO STATIONS 

To receive time signals an aerial about 500 feet long 
is desirable though a much smaller one will do. A coil 
receiver as described in Chapter III is ideal for this pur- 
pose. Apparatus described in this book will bring in the 
signals with either a crystal or audion type of detector. 
The following advice is given by the U. S. Dept. of Com- 
merce : 

Time signals are now sent out on the Atlantic coast 
only through the radio stations at Arlington, Key West, 
and New Orleans. Signals from Arlington and Key 
West, which reach a zone formerly served by other coast 
stations, are sent out every day in the year twice a day, 
viz., from 11.55 a. m. to noon and from 9.55 to 10 p. m., 
seventy-fifth meridian time. Time signals from New 

357 



358 Experimental Wireless Stations 

Orleans are sent out daily, including Sundays and holi- 
days, commencing at 11.55 a - m -> seventy-fifth meridian 
time, and ending at noon. 

On the Pacific coast the time signals are sent broad- 
cast to sea through the naval radio stations at Mare Is- 
land, Eureka, Point Arguello, and San Diego, Cal., and 
at North Head, Wash. The controlling clock for each 
station is in the naval observatory at the Mare Island 
Navy Yard. Signals from Mare Island are sent out 
every day from 11.55 t0 noon, and from 9.55 to 10 p. m., 
one hundred and twentieth meridian standard time. 
Those from North Head, Eureka, Point Arguello, and 
San Diego are sent out daily, excluding Sundays and 
holidays, from 11.55 to noon, one hundred and twentieth 
meridian standard time. 

To get the maximum clearness of signals, the receiv- 
ing circuit should be tuned to that of the sending station. 
Arlington and Mare Island send on a 2,500-meter wave 
length, North Head and San Diego on a 2,000-meter 
wave length, Eureka on a 1,400-meter wave length, Key 
West and New Orleans on a 1,000 meter wave length, 
and Point Arguello on a 750-meter wave length. 

TRANSMISSION OF WEATHER REPORTS BY 
NAVAL RADIO STATIONS 

Through co-operation with local offices of the United 
States Weather Bureau, weather forecasts are sent 
broadcast to sea through naval coast radio stations at 
certain times, varying with the locality. Storm warnings 
are sent whenever received and the daily weather bul- 






Transmission of Weather Eeports 359 

letins are distributed by the naval radio stations at Ar- 
lington, Va., and Key West, Fla., a few minutes after the 
10 p. m. time signal. These bulletins consist of two parts. 
The first part contains code letters and figures which 
express the actual weather conditions at 8 p. m., seventy- 
fifth meridian time, on the day of distribution, at certain 
points along the eastern coast of North America, one 
point along the Gulf of Mexico, and one at Bermuda. 

The second part of the bulletin contains a special 
forecast of the probable winds to be experienced a hun- 
dred miles or so ofr" shore, made by the United States 
Weather Bureau, for distribution to shipmasters. The 
second part of the bulletin also contains warnings of 
severe storms along the coasts, as occasions for such 
warnings may arise. 

Immediately following this bulletin, a weather bul- 
letin for certain points along the Great Lakes is sent 
broadcast by the naval radio station at Arlington, Va., 
consisting of two parts. The first part contains code let- 
ters and figures which express the actual weather condi- 
tions at 8 p. m., seventy-fifth meridian time, on the day 
of distribution, at certain points along the lakes. The 
second part of the bulletin contains a special forecast 
of the probable winds to be experienced on the lakes, 
during the season of navigation — about April 15 to De- 
cember 10. 

The points for which weather reports are furnished 
are designated as follows : For Atlantic coast and Gulf 
points. S=Sydney, T=Nantucket, DB^Delaware 
Breakwater, H=Hatteras, C=Charleston, K=Key 
West, P=Pensacola, and B=Bermuda; for points on 



360 



Experimental Wireless Stations 



the Great Lakes, Du=Duluth, M= Marquette, U= 
Sault Ste. Marie, G=Green Bay, Ch=Chicago, L= 
Alpena, D=Detroit, V= Cleveland, and F=Buffalo. 

All bulletins begin with the letters U. S. W. B. (United 
States Weather Bureau) and the weather conditions 
follow. The first three figures of a report represent the 
barometric pressure in inches (002=30.02) ; the next 
figure, the fourth in sequence, represents the direction 
of the wind to the eight points of the compass: i=north, 
2=northeast, 3=east, 4=southeast, 5=south, 6=south- 
west, 7= west, 8=northwest, and o=calm. The fifth 
figure represents the force of the wind on the Beaufort 
Scale, given on page 255. 



BEAUFORT SCALE OF WIND FORCE 



Number and designation 

Calm 

1 Light air 

2 Light breeze 

3 Gentle breeze 

4 Moderate breeze 

5 Fresh breeze 

6 Strong breeze 

7 Moderate gale 

8 Fresh gale 

9 Strong gale 

10 Whole gale 

11 Storm . ., 

12 Hurricane 



Nautical 
Statute miles miles per 
per hour. hour. 



0to3 


to 2.6 


8 


6.9 


13 


11.3 


18 


15.6 


23 


20.0 


28 


24.3 


34 


29.5 


40 


34.7 


48 


41.6 


56 


48.6 


65 


56.4 


75 


65.1 


90 


78.1 


and over. 


and over. 



In order to simplify the code, no provision has been 
made for wind force greater than 9, strong gale, on the 
Beaufort Scale. Whenever winds of force greater than 9 






Examples of Code 



361 



occur, the number representing them is given in words 
instead of figures, thus: Ten, eleven, etc. 

EXAMPLE OF CODE 

U S W B DU95826 M 97635 U 00443 G 96046 Ch 
95667 L 00644 D 00842 V 01054 F 01656. 

TRANSLATION 

United States Weather Bureau. 



Station. 



Pressure. Direction. 



1 See Beaufort scale. 



Force. 1 




CHAPTER XXVI 
Radiocommunication Patents 



A List of Patents for System and Apparatus; Discussion of 
Some Patents. 



U. S. PATENTS ON WIRELESS TELEGRAPHY, 
TELEPHONY, AND CONTROL 

This is the most complete list available outside of the 
Patent Office itself. It should be invaluable to the reader. 
Patents from 1881 to January 1, 1916, are included. 
Owing to conditions arising from the war which caused 
many improvements to be withdrawn from publication, 
the list is not extended since then because at best it would 
be incomplete. 

HOW TO USE THE LIST 

Look for the subject of interest or the headings that 
might contain it. Patents considered of particular im- 
portance have been designated with a * mark. Copies 
complete of any of these patents can be obtained for 
10 cents each by addressing the Commissioner of Pat- 
ents, Washington, D. C. 1917, 1918 and 1919 patents 
can be had from this address also. 

362 



U. S. Patents 



363 



GENERAL APPARATUS AND SYSTEMS, 
AND SENDING. 



BOTH TRANSMITTING 



For any other apparatus or arrangement of circuits consult also this 
general list, as it includes patents treating of more than one related 
idea. 



Patents 


numbered 












586,193 


716,334 


1,123,118* 


1,120,054 


711,266 


711,184 


717,773 


717,769 


717,771 


717,772 


711,183 


711,182 


749,584 


748,597* 


734,048 


730,247* 


743,999 


749,37a 


749,131 


737,170* 


800,854 


12,073 


758,842 


706,718 


756,904 


730,819* 


756,719* 


802,981 


805,412 


716,334 


765,298 


706,742* 


710,355 


710,354 


703,842 


768,301* 


710,122 


706,746* 


706,745 


706,743 


706,500 


763,893 


706,741* 


671,406 


711,132* 


11,952 


700,250* 


671,407 


680,001 


757,559* 


687,440 


737,072 


699,158 


795,762 


682,974 


684,706 


706,736* 


684,467 


758,005* 


750,496 


753,863* 


720,568* 


708,071 


609,154* 


711,130 


708,072 


12,168 


703,712 


706,737 


706,740 


707,064 


717,766 


743,056* 


750,429* 


671,732 


696,715 


685,742 


741,622 


763,772* 


716,203 


717,765 


768,003* 


674,846* 


664,869 


377,879 


671,176 


550,510 


657,224 


651,361 


651,362 


650,255 


651,014 


650,110* 


650,109 


647,009* 


657,222 


711,174* 


644,497 


627,650* 


647,007* 


647,008* 


643,018 


673,553 


673,418 


716,203 


671,403 


929,745 


783,923* 


781,823 


716,000 


962,014* 


934,883 


935,721 


842,910 


. 837,616 


937,901* 


841,386 


889,790 


889,792 


884,109* 


889,791 


884,070 


884,076 


957,282* 


884,108 


884,106* 


962,017 


884,071 


899,239 


899,243 


1,129,821 


728,243 


701,256 


884,986* 


729,797 


768,778 


1,006,786 


1,128,210 


730,246 


897,278* 


879,409 


913,718 


998,567* 


908,816* 


994,191 


706,738 


717,770 


894,378 


754,058 


727,329 
752,895 


727,330 


730,753 


767,979* 


767,983 


927,641 


770,668* 


874,745 


, 768,000 


884,987* 


802,430 


783,992* 


786,132* 


770,229 


759,216 


767,984 


759,825 


711,444 


760,463* 


725,635 


749,434 


749,178 


742,779 


1,162,830 


12,169 






General Systems, Continued. 






Patents 


numbered: 












706,737 


767,990* 


767,985* 


767,991* 


725,634* 


767,989* 


767,988* 


734,476 


753,864 


808,641* 


768,003 


818,236 


771,818 


767,978 


923,963 


764,093 


974,762* 


966,705* 


764,094 


1,111,777 


929,145 


926,936 


879,532 


997,515 


1,059,666* 


1,106,875 


1,038,506 


1,106,874 


899,240 


986,651 


935,382* 


916,301 


827,524 


884,107 


858,569 


1,020,032* 


1,132,568* 


1,019,236* 


1,080,271* 


1,018,555 


813,914* 


954,640* 


979,276 


808,594* 


802,432* 


1,074^23* 


996,090 


996,088 


1,001,227 


706,740 


1,157,094 


767,987* 


767,980* 


767,986 


767,981 


767,975 


725,636 


767,997* 


767,976* 


758,517 


781,873 


781,873 


813,975 


802,417 


768,005 


768,002 


767,996* 


929,349 


1,018,555 


759,826 


768,004 


884,989* 


864,272 


884,110 


935,383 


956,165 


706,735* 


798^50 


913,528 


793,652 


1,014,002* 


946,168 


934,875 


929,487 


1,031,698 


1,101,915* 


824,003 


899,242 


889,289 


822,936 


937,281 


1,010,669 


924,560* 


928,962 


1,016,003 


1,101,533* 


1,015,881 


1,003,375 


1,006,635 


1,006,636 


1,012,456 


758,527 


761,450 


802,418 


739,287 


1,020,032 


797,544* 


730,753* 


742,780 


1,002,049 


958,006 


749,372 


824,676 


767,995 


768,001 


767,997 


767,992 


767,998 


767,993 


829,787 


908,742 


901,649 


992,042 


711,131 


785,803 


711,445 


962,018 


624,516* 


797,169* 


1,128,210 


1,045,781 


1,132,569* 


1,114,840 


1,138,652 


928,371* 


956,489 


946,166 


851,621 


854,813 


869,714 


899,241 


714,648 


1,050,728 


1,074,456 


1,059,665 


1,082,221 


1,035,334 


716,334 


730,819 


1,123,119 


1,139,226 


14,012 


806,966 


756,720 


788,477 


843,733 


776,337 


782,181 


787,780 


755,846 


771,819 


792,528* 


767,999* 


767,994 


943,969 


935,386 


946,167 


965,060 


1,002,051* 


915,280 


996,580 


995,339 


929,145 


711,181 


1,127,921* 


1,101,914* 


1,014,002* 


802,431 


802,421 


802,420* 


802,419* 


444,678* 


818,363 


840,909 


992,791 


676,332* 


680,002 


716,000 


713,700 


758,004 


714,246 


960,304 


850,917 


1,021,132 


1,045,782 


1,080,554 


1,050,441 


1,022,540* 


750,216 


918,306 


918,307 


777,014 


1,158,123 



364 Experimental Wireless Stations 

receiving devices, systems, and circuits. 

Includes selective arrangements, interference compensators, beat re- 
ceivers, audio-tuning, bridge circuits, apparatus arrangements, static 
shields, etc. See also related headings. Includes some detectors. 

Patents numbered: 



1,895,342 


1,138,147 


1,144,968 


1,116,183 


1,116,588 


1,019,236* 


657,223 


1,113,149* 


997,516* 


1,134,593 


1,132,588* 


1,139,632 


1,143,799 


1,123,910 


1,127,368 


727,327 


762,829 


767,971 


801,118 


796,800 


767,922 


761,258 


712,764 


806,052 


962,417 


668,315* 


974,838 


793,648' 


921,531* 


727,331* 


995,312 


936,258 


12,115 


962,016 


665,957 


780,842 


802,613 


897,779 


962,015 


962,016 


. 845,316 


836,531 


883,437 


936,258 


962,015* 


958,181* 


974,986 


974,538 


921,531* 


902,613 


936,163 


912,726 


974,985 


892,312 


706,742 


730,246 


761,258 


727,331 


884,988 


748,306 


796,403 


12,115 


749,371* 


727,328* 


746,557* 


745,463 


737,271 


744,936 


756,219 


755,586 


773,171 


773,340 


774,922 


775,050 


782,422 


793,648 


780,842 


783,712 


961,645* 


1,002,150 


758,468 


905,537 


897,779* 


924,827 


888,191 


959,510 


982,312 


896,139 


877,451* 


883,241 


886,154 


1,009,317 


963,173 


916,429* 


918,618 


974,927 


1,012,496 


952,403 


784,762 


931,586* 


925,921 


802,428* 


824,682* 


930,508 


846,414 


852,381* 


853,929 


839,029* 


706,745 


730,247 


802,423* 


802,422* 


823,699* 


857,375 


994,426 


858,668 


846,081* 


785,276 


1,009,106 


812,557 


820,169 


816,205 


962,417 


1,093,240 


1,087,113* 


1,104,256* 


1,089,091 


13,798 


1,042,778 


1,097,974 


1,027,238 


1,091,127 


1,099,865 


1,059,391* 


1,022,539 


1,044,637* 


1,087,892 


1,087,549* 


1,132,568 


916,429 


897,278 


752,894 


752,895 


1,018,155 


1,012,496 


716,135 


167,970 


1,156,677 


1,163,839 














SELECTIVE 


SECRECY 


SYSTEMS. 








(See 


also others.) 






Patents 


numbered : 












1,102,442 


1,091,768 


714,384 


715,203 


717,978 


714,756 


795,840 


750,894 


727,326 


12,149 


714,831 


12,141 


1,123,119* 


777,014 


910,718 


768,001* 


1,091,768 


1,214,022* 









DETECTORS. 

Oscillation Responding Devices, Rectifiers, Electrolytic, Heat, Contact, 
Capillary Devices, etc. 

(For circuit arrangements, etc., see Receiving Apparatus and Systems.) 

OSCILLAPHONE. 

Patents numbered: 769,005 819,779 

MAGNETIC DETECTOR. 

772,878 877,069 917,104 930,780 711,182 917,104 749,371 

715,043 

ELECTRO- CAPILLARY DEVICES. 

Patents numbered: ^^ 

844,080 798,484 798,483 798,482 798,481 848,083 

ELECTROLYTIC 



Patents 


numbered : 












706,742 


716,334 


929,784 


894,317* 


875,105 


902,569 


795,312 


894,317 


875,105 


962,014* 


783,712 


716,203 


727,331 


716,000 


731,029 


706,744 


916,428 


793,648 


768,003 







U. S. Patents 



365 



Patents numbered: 



HEAT DETECTOR. 
800,856 767,996 767,997 

BOLOMETER. 



Patents 


numbered: 












778,275 


767,992 


767,980 


767,971 


767,981 


767,972 






CRYSTAL 


AND MISCELLANEOUS-ALL 


, TYPES. 




Patents 


numbered: 












879.062 


879,117 


923,700 


924,827 


837,616 


886,154 


912,613 


912,726 


1,159,969 


1,152,444 


1,158,112 


11162,765 


1,080,681 


1,052,355 


1,096,142* 


1,048,117 


1,102,184 


1,104,065 


1,104,073* 


867,876* 


899,264 


824,637* 


824,638* 


927,314 


1,013,223 


986,806 


966,855 


954,619 


959,967 


867,878 


867,877 


912,613 


879,062 


917,574 


1,004,784 


904,222 


906,991 


811,654 


776,359 


757,802 


701,570 


1,003,210 


905,781 


901,942 


962,262 


836,070* 


836,071* 


1,155,338 


879,061 


820,258 


902,569 


706,744 


707,266 


771,123 


756,676 


787,412 


1,003,374 


902,569 


1,136,044 


1,136,045 


1,137,714 


1,136,046 


1,136,047 


1,122,558 


1,128,552 


1,118,228 


1,115,902 


1,112,411 


1,145,658 


1,144.399* 


1,008.977* 


933,263 


770,228 


917,574 


706,735 


706,736 


767,985 


837,616 


706,735 













MERCURY AUDION, VACUUM VALVES, AUDIONS, THERMIONIC 
RELAYS, AND DETECTORS. 

Patents numbered: 



1.130,008 

837,901 

1,127,371* 

1,145,735 

943,969 

837,901 


1,142,625 

867,876 

1,430,008 

1,144,596 

824,637 

841,387 


837,878 
995,126 
1,128,817 
1,159,307 
824,638 
867,877 


836,070 

836,071 
1,130,009 
1,138,652 

867,071 

867,878 

COHERERS. 


879,432 

979,275* 

1,130,042* 

1,113,149 

915,280 


841,386 
802,689* 
1,128,280 
841,397 
824,637 


979,275 
1,130,043* 
1,137,275 
1,156,625 

803,684 






(See Radio-Mechanical 


Control.) 






Patents numbered 
1,019,260 932,788* 
800,119* 908,504 
968,007 670,711 
741,767 1,118,410 


700,708 

985,854 

708,070 

1,150,111 


691,815 
775,113 
755,840 


993,024 
742,298 
722,139* 


886,983 
763,894 
710,372 


794,459* 
759,835 
1,019,260 



WAVE METERS. 

Patents numbered: 

804,189 1,064,325 1,018,769 804,190 932,819 

892,311 993,316 1,152,632 

GALVANOSCOPE. 

Patent numbered 798,152 

SYLCHRONIZER. 

Patent numbered 717,768 

RANGE FINDER. 

(See also Direction Finders.) 

Patents numbered: 749,436* 1,135,604* 



846,675 



918,256 



366 Experimental Wireless Stations 

spark gaps, including muffled, cooling and tone 

TYPES. 

Patents numbered: 
1,073,371 1,051,744 1,075,075* 834,054 926,933 971,935* 1,132,589* 

1,117,681 750,180 750,005 1,163,586 792,014 706,741 768,000* 

1,148,521* 1,161,520 1,152,272 1,162,659 

WIRELESS TELEPHONY. 

(See also Oscillation Producers, Transmitting- and Sending Systems, etc.) 

Patents numbered: 

1,118,004 1,125,496* 1,122,594 1,139,413 1,062,179* 1,086,530 1,107,985* 

1,044,798 1,052,849 1,088,686 803,199* 836,015* 814,942 836,072* 

803,513* 1,006,429 923,962 753,863 793,649 793,750 1,148,827 

RADIO=MECHANICAL CONTROL. TORPEDOES, TYPEWRITERS, 
ETC., CONTROLLED BY WIRELESS. COHERERS. 

(See also Detectors and Systems.) 

Patent numbered: 

715,803 1,115,530* 1,097,871 1,072,152 1,987,966 625,823 1,029,573 

789,618 976,500 828,864 907,488 1,098,379* 957,001 663,400 

723,176 913,814 1,155,653 1,154,628 1,149,874 

RECEIVING RECORDER. 

Patent numbered 766,743 

RELAYS AND RELAY SYSTEMS. 

Patent numbered: 

717,514* 786,696* 657,221* 718,535 717,513 717,509 717,570 

1,106,729 655,716 

AUTOMATIC TICKER. 

(See also Receiving Devices.) 

Patents numbered: 1,098,380 1,161,142 

TUNING DEVICES AND COUPLINGS. 

(See also Receiving Systems, Transmitting Systems, Wavemeters.) 

Patent numbered: 

1,116-,130 978,604 802,425 1,070,376 1,014,722 1,014,722* 1,083,085 

1,096,065 719,005 707,056 763,345* 717,511* 934,296 803,569 

956,936 996,082 717,512* 1,132,568 1,127,921 714,756 714,831 

1,151,098 1,148,279 

AMPLIFIERS FOR RECEIVING. 

(See also Receiving Systems, and Audions.) 

965,884 714,832 1,041,210 12,151 12,152 1,163,180 751,818 

714,833 1,165,454 

ALARM SYSTEM. 

See Coherers, and Radio-Mechanical Control.) 

Patent numbered 606,405 

CONDITION AND EARTH SYSTEMS. 

(See general system list.) 

Patents numbered: 1,051,443* 690,151 • 



U. S. Patents 367 

COMBINATION SETS. RECEIVING AND TRANSMITTING LINE 
AND RADIO. 

Patents numbered: 996,089 1,104,712 1,092,294 916,483 972,721 

PORTABLE STATIONS. 

(See general list and Aerials.) 

Patents numbered: 1,145,066 958,209 

COMBINATION TRANSMITTING AND RECEIVING SETS. 

(See also general list.) 



Patent 


numbered: 












116,111 


1,141,453 


1,141,386 


751,294 


777,014 


736,483 


726,413 


840,908 


979,144 


916,985 


876,281 


794,334 


798,158 


810,150 


793,652 















TRANSFORMERS RESONANT WITH CAPACITY, FOR TRANS- 
MITTING STATIONS. 

Patents numbered: 965,168* 835,023* 

DIRECTION AND DISTANCE FINDERS. 



Patent 


numbered: 












736,432 


744,897 


716,135 


1,069,355 


899,272 


12,148 


941,565 


943,960* 


961,265 


984,108 


948,086* 


945,440* 


894,318 


1,002,141 


833,034 


716,134 


758,517 


1,149,123 


1,149,122 







STATIONARY AND PORTABLE ANTENNA— AEROPLANE, 
AERIALS. 

Patent numbered: 



,141,387 
959,100 

,101,175 
770,229 


918,255 
1,005,471* 
1,063,671 

749,436 


919,115 

793,718 

1,132,569 

749,131 


930,746 
793,651 
767,973 
748,697 


898,197 
948,068 
717,511 
771,819 


945,475 
860,051 
706,737 
707,746 


972,004 
1,106,945 
1,147,010 

706,738 






Aerials, Continued. 






706,739 
802,981 
767,988 


716,136 
802,982 
767,999 


899,272 
806,066 
716,177 


1,158,124 

822,936 

1,165,412 


717,512 
824,003 


793,718 
767,986 


753,864 
767,988 



BREAKING SYSTEMS AND KEYS— SENDING TO RECEIVING. 

Patents numbered: 827,523 842,134 1,016,564* 1,073,624 

MASTS— AERIAL SUPPORTS, INCLUDING AEROPLANE AERIAL 
DEVICES. 

Patents numbered: 1,116,059 857,152 1,034,760 1,099,861 768,005 

AUTOMATIC CHANGE=OVER SWITCH-SENDING TO RECEIVING. 
Patent numbered 1,074,057 

CLEARING ICE FROM ANTENNAS. 
Patent numbered 750,181 



358 Experimental Wireless Stations 

protecting devices. 

Patents numbered: 771,820 978,607 1,035,958 

CONDUCTOR FOR WIRELESS TELEGRAPHY. 

Patent numbered 706,739 

CURRENT INTERRUPTER. 

(General interrupters not included.) 

Patent numbered 1,039,011 

KEYS, CIRCUIT CLOSERS AND CONTROLLERS. 

917,749 792,020* 792,015 769,228 934,716 749,178 792,015 

TRANSMISSION OF MUSIC. 

(See Radiotelephony.) 

Patent numbered 1,025,908 

PUNCHED TAPE SYSTEMS. 

Patent numbered: 

725,634 725,635 725,636 767,978 767,991 767,932 767,995 

STATIC VALVE. STATIC PREVENTION. 

Patents numbered: 823,402 825,402 

METHOD OF UTILIZING ENERGY OF WAVES. 

(See general list.) 
Patent numbered 731,029 

VISIBLE AND AUDIBLE SIGNAL. 

(See Coherers, Radio-Mechanical Control, etc.) 
Patent numbered 805,714 

COMMUNICATION BY WAVE COMPONENTS. 

(See also General Systems.) 

Patent numbered 876,996 

PRODUCTION OF TONE EFFECTS. 

(See also Spark Gaps, General Systems, Transmitters.) 

Patents numbered: 1,056,892* 1,056,893* 
AUTOMATIC COMMUTATOR FOR WIRELESS TELEGRAPHY. 

(See General Systems also for similar arrangements.) 
Patent numbered 1,105,029 

RELAYING HIGH FREQUENCY CURRENTS. 

(See also Audions, Detectors, Oscillation Producers, etc.) 
Patent numbered 1,042,069* 



U. S. Patents 369 

DETERMINATION OF FREQUENCY. 

(See also Wavemeters.) 

Patent numbered 1,022,584 

SYSTEMS OF HIGH FREQUENCY DISTRIBUTION. 

(See also general Systems, Transmitters, Oscillation Producers.) 

Patent numbered: 
1,123,098* 1,122,027* 856,140* 856,150* 1,043,104* 1,043,766* 

CONTROL OF SPARK PRODUCTION. 

(See also Radiotelephony and General Systems.) 

Patents numbered: 750,180 802,850 

TELEPHONE RECEIVER. 

(General telephone list not included.) 

Patent numbered 936,684 

DUPLEX, MULTIPLEX, SYSTEMS, 

(See General Systems.) 

716,136 772,829 802,429 802,426 717,767 767,970 924,168* 
1,116,309* 1,076,312 1,042,205 749,434 720,568 716,134 772,879 
767,980 716,134 793,652 

SUBMARINE SIGNALLING SYSTEMS, COLLISION PREVENTION, 

ETC. 

711,386 1,126,095 1,073,088 749,694 802,020 914,483 913,910 

526,609 1,099,998 

PHOTOPHONES. 

(See General Systems.) 

Patent numbered: 

235,120 680,614 796,254 766,355 241,909* 235,496* 235,199 

341,213 

CONDENSERS, PAPER, GLASS, AIR, COMPOSITION, ETC. 

(For complete list see general electrical classification omitted here.) 

Patent numbered: 

1,127,513 793,647* 786,578 793,777 1,033,095 1,150,895 1,108,793 

1,063,105 1,094,178 1,116,013 1,111,289* 1,112,397 1,114,626, 1,139,976 

814,951 793,647 793,651 767,977 1,151,824 

DIRECTIVE SYSTEMS. 

Patent numbered: 

795,762 749,131 720,568 716,134 716,135 771,818 771,819 



370 Experimental Wireless Stations 

transmission systems and apparatus. 

(General list. See also detail lists, as they are not repeated here.* 
See General Systems.) 

1,145,239— Polvnhase 97 

586,193 

749,435 

755,132 

935,381 
1,119,732 

953,635 

917,103 
1,141,717 

714,837 

767,979 1,153,717* 

OSCILLATION PRODUCERS, ARC CONTROLS, PRODUCTION 

OF HIGH FREQUENCY CURRENTS AND ALL KNOWN 

TYPES OF WAVES. 

(See Audions and General systems. This list includes mercury vapor 
devices applied to the art, except such as are listed elsewhere.) 

Patent numbered: 



lyphase 


974,169 


1,119,952 


247,127 


255,305 


11,913 


657,363 


465,971 


932,821 


926,900 


767,974* 


767,973* 


685,953 


685,954 


685,957 


785,956 


754,737 


767,977 


775,416 


776,876 


876,165 


792,014 


787,056 


910,430 


950,258 


932,820 


921,293 


1,005,338 


986,405* 


918,208 


749,372 


802,850 


768,004 


758,004 


1,148,279 


966,539 


927,433 


802,427* 


851,336* 


991,937 


834,497 


966,475 


858,554 


1,015,881* 


921,013 


1,136,411* 


1,139,226 


1,140,150 4 


,126,966* 


723,188 


685,958 


685,955 


714,832 


714,833 


767,990 


767,975 


767,976 


767,984 


767,989 


767,975 



550,630 


1,115,823 


1,118,174 


1,121,360 


1,120,306 


829,447 


829,934 


1,097,872 


1,087,126 


1,152,675 


500,630 


1,122,975 


1,131,190 


1,123,120 


1,139,673 


790,250 


1,023,135 


1,043,117 


1,101,148 


1,159,209 


1,142,496 


717,774 


685,012 


925,060 


1,047.643 


1,103,822 


1,101,491 


1,061,717 


921,526 


979,277 


780,997 


773,069 


1,096,717 


1,105,984 


1,092,398 


1,110,253 


781,606 


817,137 


932,111 


966,560 


1,077,733 


1,028,204 


1,709,909 


923,963 


730,755 


758,004 


706,742 


897,279 


767,983 


767,993 















RELAY OF MESSAGE. 

Patents numbered: 717,509 717,513 717,514 717,516 

NOTES ON LIST. 

As a guide to date of issue, the number of the first patent for a period 
is given herewith: 
747,127-1881 691,176-1902 730,247-1903 749,131-1904 802,417-1905 

808,641-1906 840,909-1907 876,165-1908 908,742-1909 945,440-1910 

984,108-1911 1,014,002-1912 1,050,728-1913 1,083,667-1914 1,123,910-1915 
Numbers of five figures, as 12,073, are for re-issued patents. 
The author assumes no liability for the accuracy of the list. The gen- 
eral list of electrical patents which overlaps the radio list in many 
instances has not been included because it alone is far larger than the 
entire wireless list. 

DISCUSSION OF SOME OF THE U. S. PATENTS 
LISTED 

By way of pointing out indications of progress a few 
of the patents may be mentioned. Patents numbered 
1,087,113 and 1,104,256 describe the tone wheel ticker 
receiving system of Rudolf Goldschmidt. Patents num- 
bered 1,098,379, 1,154,628 and 1,115,530 describe the con- 






Discussion of the U. S. Patents Listed 371 

trol system of J. H. Hammond, Jr. An improved audion 
circuit is given in patent 1,113,149 of E. H. Armstrong. 
An arc oscillator using an arc between cooled electrodes 
immersed in alcohol and said to have transmitted tele- 
phone communication 600 miles is set forth in Dwyer's 
patent No. 1,109,909. A multiphase transmitter is de- 
scribed in patent 1,114,840. A practical arrangement of 
an aerial on an aeroplane is given in patent numbered 
1,116,059. The duplex system of Marconi using two 
aerials at right angles is explained in patent numbered 
1,116,309. A receiving set which is selective and ob- 
viates the use of the loose coupler by a practical arrange- 
ment of inductance and capacity is described in Cohen's 
patent No. 1,123,098. A proposed secrecy system is 
described by De Forest in patent numbered 1,123,119. 

A suitable system for radiotelephony over about fifteen 
miles is described by De Forest in patent 1,125,496. His 
arrangement uses a quenched spark gap oscillator. A 
balanced receiving circuit which attempts to prevent in- 
terference is described in patent 1,127,368. A good 
tuning circuit for receiving with both tight and loose 
coupling is described in Tronchon's patent 1,129,821. 
Weintraub furnishes much information on mercury 
vapor tubes as oscillation producers in patent numbered 
1,131,190. Tape sending and phonographic recording is 
illustrated in Fessenden's patent 1,132,568. Marconi 
describes a plural circuit rotary gap method of generating 
continuous waves in patent 1,136,477. R. C. Galletti 
shows a system utilizing high frequency unidirectional 
impulses in patent 1,140,150. A novel aerial loaded with 
inductance and capacity to give a large wave-length 



372 Experimental Wireless Stations 

range in a small space is illustrated by Franklin in patent 
1,141,387. A good exposition of the heterodyne system 
is given in patent 1,141,717. Patent 1,144,969 shows a 
method of using a crystal detector to receive from un- 
damped wave stations. P. C. Hewitt describes his mer- 
cury vapor receiving system in detail in patent 1,144,596. 
Marconi explains his disk discharger in patent 1,148,521. 
An improved coheror is illustrated in patent 1,150,111 
and a new manner of using it for radio control is shown 
in patent 1,155,653. Seibt describes a practical quenched 
spark transmitter in patent 1,153,717. Vreeland illus- 
trates his mercury arc generator cooled by water in patent 
1,152,675. An antimony and ferro-silicon detector is 
shown in patent 1,158,112. A-secrecy method is shown 
in patent 14,012 of Nov. 16, 191 5. The receiving ticker 
used by the Federal Telegraph Co. is shown in patent 
1,161,142. Quenched spark gap construction is the sub- 
ject of Pfund's patent 1,161,520. In patent 1,152,272 H. 
Boas makes the practical suggestion of using tungsten for 
spark gaps. One form of the plural receiving tuner men- 
tioned on page 252 is described in patent 1,151,098. A 
practical quenched spark system is described in patent 
1,162,830. Amplification by means of microphones in 
cascade is explained in patent 1,163,180. Patent 1,127,371 
shows how an audion may be used in connection with a 
relay circuit for wireless control purposes. Patent 
1,165,412 shows a practical installation of a wireless set 
on an aeroplane, but employs the objectionable hanging 
wire antenna. Patent 1,214,022 shows some interesting 
improvements by P. Edelman. 



CHAPTER XXVII 
Rights of the Experimenter 

Information on Complete Sets; List of Radio Stations; The 
Law of 1912; How to Get Licenses; Radio Inspectors; 
Rules for Operating; Patents; Tendency of Art; Wire- 
less Codes; Conclusion. 

The completed receiver, of whatever type adopted, can 
all be mounted together if desired. In any case the con- 
nections used should be of stranded insulated conduc- 
tors, kept free from each other, .well insulated from wood 
and other matter, the switch contacts clean, and so on. 
The descriptions have been made as clear and concise as 
possible, though the details have been purposely left to 
the individual in many cases where the design is optional. 
Such items as cases, boxes or mountings are well within 
the limits of every reader, and even in the other apparatus 
and parts considerable ingenuity may be used. Duplica- 
tion of apparatus has been avoided wherever possible, 
though in some cases all forms have been described. 
When one piece of apparatus will do the work of two, 
there is little use in using two. Every piece of appa- 
ratus should be made with care and should always be 

373 



374 Experimental Wireless Stations 

understood. Learn to know your apparatus, master its 
peculiarities, note the good and bad adjustments, always 
be on the lookout for possible phenomena, and keep a 
record of your experiments. While the apparatus de- 
scribed is intended particularly for stations it can be 
easily made portable. Stations may be readily set up 
on small boats, in the field, camp, and so on. There is 
hardly a limit to the use to which a wireless set may be 
put. 

The experimenter generally plans to receive over a 
much greater distance than he expects to send. Indeed, 
with the present network of high-powered stations, there 
are few readers who may not do long distance work with 
even simple apparatus. The Arlington station, "NAA," 
for instance, should be heard by every experimenter 
within 1,000 to 3,000 miles under favorable conditions. 
It is surprising to learn what can be done with even 
home-made apparatus. A list of wireless stations may be 
obtained for 15c by addressing the Superintendent of 
Documents, Washington, D. C. 

If you have not already done so, join a local wireless 
club. Nearly every locality has one or is forming one 
and there is little or no expense attached. If you have 
not yet learned a code, start now. The continental code 
is in general favor and it is well to master it first. It is 
the one wireless code in universal use. There are so 
many messages which can be read with a simple receiv- 
ing set, that the code can be mastered in a short time. 
In practice, it is well to start with the letters first, then 
with short words, and finally with simple sentences and 
paragraphs. The average person finds it much easier to 



Rights of the Experimenter 375 

send than to receive. Acquire a free, easy and clear 
movement in making the dots and dashes. Speed is a 
secondary matter, as it will come with practice. It is 
worth while to keep a record of all messages in a small 
note book. It is unlawful to give out or publish inter- 
cepted messages. 

THE EXPERIMENTER'S RIGHTS 

All of the leading countries have laws regulating 
radiocommunication. The wireless law enacted on De- 
cember 13, 191 2, makes the following restrictions upon 
experimenters : 

1. The law recognizes the experimenter, gives him rights, 
and licenses are to be given provided that, 

2. The experimenter does not use a wave length over 200 
meters long for transmission nor a greater power in either a 
coil or transformer than 1 K. W., if he is farther than 5 nauti- 
cal miles away from a government station, or not more than 
y 2 K. W. if he is within 5 nautical miles of a government 
station. 

3. Experimenters having apparatus which is not powerful 
enough to transmit farther than the boundaries of the state 
in which the station is situated, and which cannot interfere 
with the reception of signals from outside the state, need 
not take out a license unless they desire to do so. This 
means practically that if you live in the heart of say Texas, 
you may use large power without license provided stations 
in other states cannot hear you, but if you live near the 
border of another state you must use very weak power or 
else obtain a license. 

4. It is not necessary to have a license for a receiving 
station only. 

5. If the experimenter wishes to use a high wave length 
or high power, permission will be granted by the Secretary 



376 Experimental "Wireless Stations 

of Commerce and Labor, upon proper application, provided 
the applicant shows cause why the additional power and 
wave length is desired. 

6. The operator is required to preserve the secrecy of all 
messages sent or received upon the penalty of a fine and im- 
prisonment. 

7. The experimenters must use sharp and pure waves. 

8. The penalty for sending a false message of any kind 
will be a fine up to $1,000 or imprisonment up to two years 
or both. (Distress signal, $2,500 — 5 years.) 

9. The operation of wireless instruments 'for either send- 
ing or receiving except as before stated, without a license, 
will be punishable by a fine of not more than $500 and the 
forfeiture of the apparatus. This does not apply to receiv- 
ing apparatus only. 

These are simple, boiled down accounts of the main 
requirements and provisions of the law as far as the 
experimenter is concerned. Information will be fur- 
nished by the Dept. of Commerce, Radio Inspection divi- 
sion without expense, upon your request. 

The licensing is free and even advantageous to ex- 
perimenters. The apparatus described in this book when 
used with reasonably loose coupling will enable the 
reader to comply with every feature of the law without 
difficulty, provided that the aerial used for transmitting 
purposes is not made longer than 70 feet by itself,* 
allowing for lead-ins to make up the remainder of the 
effective length. The plan of using a duplex aerial will 
be found particularly valuable in accordance with the 
law, so that long distance messages may be received. The 
two aerials should be placed at right angles to each 
other if possible in order to avoid unnecessary absorp- 
tion of the transmitted energy. There is no cause for 

* This allows a height of 5c to 70 feet for leads, etc. 



Patents 377 

alarm over the new laws proposed, as the act of 1912 
still stands (1920) and the value of experimenters as 
well as amateurs is recognized. The Navy Dept. closed 
all stations with few exceptions during the war but the 
emergency authorizing this has now ended and pre-war 
conditions are again fully restored. 

• 
The Department of Commerce and Labor has formed cer- 
tain rules and regulations which must be adhered to. Ad- 
ministration districts have been established, with offices at 
the custom-houses. Classifications have been made for the 
purpose of administration. Full particulars can be obtained 
gratis by addressing the Commissioner of Navigation. The 
first thing to do is to write for forms No. 756 and 757. Full 
instructions will be sent at the same time. There will not 
be any difficulties in obtaining a license, but it is imperative 
that you apply for the license at once before you operate. 
Radio Inspectors in government employ will even assist you 
when possible. 

PATENTS 

While most of the wireless apparatus is covered more 
or less completely by patents, the experimenter need have 
no concern. Although the experimenter is legally an in- 
fringer when he uses patented apparatus without per- 
mission from the patentee, it is generally recognized that 
experimenters may use patented articles for purely non- 
commercial purposes without liability. This educational 
idea seems to be so fixed that even manufacturers and 
dealers in patented experimental goods not made under 
license or permission of the patentee, are for the most 
part perfectly safe, since the patent rights are seldom 
pushed into this realm. The author certainly does not 



378 Experimental Wireless Stations 

advise the open and wilful infringement of patents, but 
also believes that for educational and experimental pur- 
poses where no commercial profits are realized from such 
use, the use of patented articles is recognized as legiti- 
mate in effect if not in the legal sense. The readers need 
have little concern on this point as long as they do not 
make or sell or rent the apparatus for commercial gain. 

While there is a large field for improvement in the 
new art, the reader is not advised to take out or apply 
.for patents unless he is sure that the device has merit, is a 
real improvement, and is needed, as otherwise failure in 
one form or another will generally result. There are at 
the present time something like 2,000 patents in full 
force which cover wireless apparatus and systems. While 
a part of these are useless and obsolete, it is not unlikely 
that the very improvement you have in mind is embodied 
in one or more of these, so that it is well to have a 
search made into the records before spending money for 
applications, models, etc. This is not intended to dis- 
courage but rather to encourage in the right direction. 

In conclusion it seems well to remark that the present 
tendency in the art is toward the permanent establishment 
of large chains of powerful land stations employing direc- 
tive aerials, the simplication of ship, train, and portabl 
stations, the use of long wave lengths for large powe 
radiation, the employment of high pitch musical tones fo 
transmission, the transmission methods which make re- 
ception inaudible except when the principle of beats is 
employed at the receiving station, the use of amplifiers to 
increase the effective intensity of the received energy, 
the use of ground receiving antennas and multi-turn 



! 



Conclusion 379 

receiving coils substituted for antennas, the extension of 
vacuum tube circuits, the use of automatic recorders, and 
a beginning toward early standardization. Among the 
new developments some brief mention of the Edelman 
Differential Wave System will doubtless be of interest. 
Experiments by the author have already shown that the 
common disturbances — undesired signals as well as 
atmospherics — do not interfere with this system. The 
promising experiments with pin point gaps, liquid trans- 
mitters, stepped-up- frequency-alternators, and low or 
even grounded aerials also deserve to be mentioned. 

The reader will do well to continue with the study, as 
much interesting and useful material of an advanced na- 
ture is to be had. 

And so, we come to the end of the book but, it is 
hoped, 

Only the Beginning of a Study of the Wonderful New 

Art. 



380 Experimental Wireless Stations 



When- One is given - tst. is Morse and Continental 
When - Two are given- 1st is Morse, 2nd Continental. 



yy •■■ MandC ^^1 ■■■ 

— # E3 -■" P 

— — ' lj - ■•■__ 

— □ _ "« R 



• •• 



,S8 F 



M ~N a 



• ••• 

Morse Only 



Fig. 167. — Wireless Communication Codes. 



INDEX 



Absorption of short and long 

waves, 17. 
Adjustment of apparatus, 174. 
Advanced systems, 187. 
Aerial, assembly, 39. 
Aerial, conductors, 39. 
Aerial, dimensions of, 29, 30, 

31. 
Aerial, duplex, 28. 
Aerial, effect of capacity, 29. 
Aerial, effect of dimensions on 

waves, 24. 
Aerial, effective length of, 29. 
Aerial, for 200 meters, 29. 
Aerial, function of, 15, 24. 
Aerial, joints for, 41. 
Aerial, lead-in, 38. 
Aerial, materials for, 40. 
Aerial, oscillation of, 14. 
Aerial, poles, 27, 28. 
Aerial, suited for 15,000 meter 

reception, 31. 
Aerial supports, kites, 26. 
Aerial switch, 126. 
Aerial, underground, 54. 
Aerials, 23. 

Aerials, balancing, 355. 
Aerials, for various wave 

lengths, 35. 
Aerials, height of, 16, 28. 



Aerials, low ground, 354. 

Aerials, makeshift, 26. 

Aerials, on ground, 26. 

Aerials, types of, 29. 

Aerials, wire for, 31. 

Aeroplane, radiotelephone, 242. 

Aeroplane wireless, 351. 

Air condenser, 318. 

Alcohol, use in spark gap, 168. 

Alexanderson alternator, 202. 

Alexanderson amplifier, 238. 

All dot system of transmis- 
sion, 169. 

Alternator, 200. 

Amateur radiophone, 248. 

Amateur Station, typical, 
Frontispiece. 

Amplifier, 274, 275, 310. 

Amplifier, cascade, 217. 

Amplifier, combined audio and 
radio frequency, 233. 

Amplifier, converted frequency, 
237. 

Amplifier, magnetic, 238. 

Amplifier, sensitive short wave, 
237. 

Amplifiers, 220. 

Antenna circuit, 71, 103. 

Antenna circuit, tuning, 75. 

Antenna current and voltage, 



Antenna, design, 103. 



381 



382 



Index 



Antennas, see aerials, 31, 33. 

Antenna, see aerial effective 
length of, 104. 

Antenna switch, 127. 

Apparatus, causes of failure, 
347. 

Arcing, prevention of, 126. 

Arc set, small, 191. 

Arc transmitter, 188. 

Armstrong circuit, 224, 226. 

Army and Navy sets, 244. 

Atmospheric disturbances, 20, 
22. 

Audibility meter, 281. 

Audibility of signal, formula, 
282. 

Audio frequency amplifier, 229. 

Audion, action of, 209. 

Audion compared with crystal 
detector, 231. 

Audion, effect of magnet on, 
222, 311. 

Audion generator, 220. 

Audion generator measure- 
ments, 185. 

Audion laboratory circuits, 235. 

Audion, noisy " B " battery, 
349. 

Audion receiver, 212, 215. 

Audion, see Vacuum tube, 210. 

Audion with crystal detector, 
231, 232. 

Autodyne receiver, 310. 

Automatic aerial switch, 127. 

Automatic indicator, 272. 

Automatic self tuned gener- 
ator, 236. 

Automatic switch, 130. 

Automatic wave changing re- 
ceiver, 308. 



Automobile wireless, 351. 
Auxiliary apparatus, 121. 
B 

"B" battery, 213. 

Balancing out power line hum, 

297. 
Baldwin receiver, 276. 
Banked turn inductances, 339. 
Barrage receiver, 303. 
Beats, 80, 304. 
Beats, illustrated, 305. 
Beats, illustration of, 89. 
Beaufort scale, 360. 
Bellini-Tosi direction finder, 

307, 353. 
Break-in system, 129. 
Bridge tuning method, 289. 
Broad wave production, 82, 83. 
Brush discharge, effect of, 140. 
Building a condenser, 318. 
Building detectors, 265. 
Building of condensers, 140, 

146. 
Buzzer test, 266. 



C, 99. 

Capacity, 133. 

Capacity and inductance, 69. 

Capacity coupling, 309. 

Capacity, formula, 136. 

Capacity for use with spark 

coils, 98. 
Capacity of aerial, 29. 
Carborundum, 258. 
Cascade amplifier, 217. 
Cascade circuits, 229. 
Centimeter, 137. 



Index 



383 



Chaffee gap, 168. 

Chalcopyrites, 258. 

Change-over switch, 126. 

Changing wave length, 289. 

Circuit, wave length of, 70. 

Circuits, measurement of, 171. 

Circuits, rotary gap, 166. 

Circuits, tests of, 186. 

Codes in use, 380. 

Coil receiver, 27, 49. 

Coil receiver, at right angles to 
each other, 50. 

Coil receiver, construction of, 
51. 

Coil receiver, principles of, 49. 

Coil receiver, use of, 51. 

Coils, inductance of, 148. 

Complete sets, 374. 

Condensers, 133, 315. 

Condenser capacity, formula, 
147. 

Condenser construction, 134. 

Condenser details, 146. 

Condenser for fine adjustments, 
324. 

Condenser materials, 142. 

Condensers, simple, 147. 

Condenser, size of, 136. 

Conflicting stations, 286. 

Construction of condenser, 316. 

Core, for transformer, sepa- 
rate tongue type, 111. 

Core, transformer, 109. 

Coupling, 288. 

Coupling, capacity, 309. 

Coupling of circuits, 106, 107. 

Coupling of radio circuits, 89. 

Crystal detector and audion, 
231. 

Crystal detector circuits, 290. 



Crystal detector compared with 

audion, 231. 
Crystal detectors, 252. 
Crystal rectifiers, 258. 
Cycles, action in transformer, 

68. 
Cycles, action on vacuum tube, 

213. 



D 



Damped and undamped waves, 
287. 

Damping illustrated, 183. 

Damping, see resistance, 86. 

Dead ends, 343. 

Dead end switch, 344. 

Decrement, 183. 

Decrement formula, 184. 

Detector, 252. 

Detector action of electron 
tube, 209. 

Detector construction, 261-265. 

Detector materials, 258. 

Detector, purpose of, 253. 

Detector, use of, 171. 

Detectors, rank of, 256. 

Detectors, see vacuum tubes, 
257. 

Diaphram for telephone re- 
ceiver, 279. 

Dielectric table, 137. 

Differential tuning, 289. 

Differential wave system, 302. 

Direct current transmitter, 192. 

Direction finder, 49, 353. 

Directional receiver, 51. 

Distance of communication, 91. 

Distributed capacity of coils, 
339. 



384 



Index 



Double humped waves, 83. 

Duplex aerial, 28. 

Duplex high speed operation, 

205, 206. 
Dynatron, 219. 



Earth, conductivity of, 13. 
Effective length of antenna, 

104. 
Efficiency of transformer, 109. 
Einthoven galvanometer, 270. 
Electrolytic interrupter, 121. 
Electron tube, see Vacuum 

tubes, 210. 
Electron tube, characteristic 

action of, 208. 
Energy, in spark transmitter, 

72. 
Energy, in wireless circuits, 73. 
Energy received, 254. 
Erg, 254. 
Experimenter's rights, 375. 



Farad, 97. 

Flat top antennas, 31, 33. 

Fleming valve, 213, 214. 

Forest fire prevention, 350. 

Formula, capacity, 136. 

Formula for audibility, 282. 

Formula for condenser capac- 
ity, 147. 

Formula for coupling, 107. 

Formula for decrement, 184. 

Formula for inductance, 148, 
150. 

Formula for 200 meter cir- 
cuit, 100. 



Formula for wave length, 99. 
Formula, transformer, 96. 
Frequency, 166. 
Frequency, conversion, 303. 
Frequency, effect of change, 97. 
Frequency, generator, 203. 
Frequency, measurement of, 

182. 
Frequency, spark rate, 95. 



Galena, 258. 

Galvanometer, Einthoven, 270. 

Gaps, operated under pressure, 

166. 
Gaps, rotary, 163. 
Gaps, simple, 165. 
Gaps, spark, 159. 
Geared adjustable condenser, 

324. 
Geissler tube, use of, 103. 
Generator, vacuum tube, 237. 
Goldschmidt alternator, 201. 
Grid circuit, 209. 
Grid control, 220. 
Grid leak, 220. 
Grid operated receiver, 220, 

221. 
Grid potential, 209. 
Grounds, connections, 58, 59, 

60. 
Grounds, imbedded, 58. 

H 

Hall jet amplifier, 275. 
Head-sets, 253. 
Heaviside layer theory, 14. 
Helix, construction, 151. 
Helix, inductance of, 149. 



Index 



385 



Henry, 99. 

Heterodyne action, 304. 
Heterodyne receiver, 303. 
High frequency generator, 199, 

200. 
High frequency oscillations, 

185. 
High power station, 354. 
Home wireless set, 246. 
"Hook-ups," 287. 
Hot wire ammeter, 105, 108, 

172. 
Hot wire meter construction, 

175, 176, 177, 178. 
Hoxie recorder, 273. 
Humidity, effect on strays, 18. 



Interference prevention, 283. 
Interferences, types of, 285. 
Interrupter, electrolytic, 121. 



Jeweller's receiving set, 300. 

K 

Keys, 124. 

Keys, magnetic operation, 125. 
Kickback prevention, 122, 123. 
Kites, as aerial supports, 26. 
Korda air condenser, 318. 



Inductance, adjustable without 
sliders, 331. 

Inductance and capacity, 69. 

Inductance and capacity for 
arc generator, 190. 

Inductance formula, 148, 150. 

Inductance, transformer, 92, 
93. 

Inductances, 148. 

Inductances, receiving, 325. 

Inductances with minimum ca- 
pacity, 69. 

Inductively coupled receiver, 
293. 

Inductively coupled transmit- 
ter, 67. 

Insulation, aerial, 36, 37. 

Insulation, importance of, 182. 

Insulators, 137. 

Interference, 19. 

Interference from power line, 
297. 



L, 99. 

L aerial, 34. 

Laboratory oscillation pro- 
ducers, 235. 

Law of 1912, 375. 

Law, wireless, 376. 

Lead-in, aerial, 38, 43. 

Legal requirements, 375. 

Lepel arc, 195. 

Lieben-Reisz tube, 215. 

Lighting circuit, protector, 123. 

Lightning protection, 61. 

List of radio stations, 374. 

Loading coil, 76, 151, 157. 

Loading coil calibration, 174. 

Logarithmic decrement, 183. 

Long wave length receiver, 226. 

Long wave length stations, 340. 

Loop receiver, 49. See coil 
receiver, 51. 

Loose coupled transmitter, 76. 

Loose coupler, 292. 



386 



Index 



Loose coupler construction, 

334. 
Loose couplers for long waves, 

342. 

M 

Magnetic blow off, 126. 
Magnetic tube sensitizer, 311. 
Making apparatus work, 346. 
Measurements of circuits, 171. 
Measurement of decrement, 

183. 
Measurements with electron 

tubes, 185. 
Measuring signal intensity, 281. 
Messages, increasing number 

transmittable, 206. 
Meter, dimension of, 99. 
Meter, 200, formulas, 100. 
Meters, 200, legal requirements 

for, 25. 
Meters, 200, long distance work 

on, 25. 
Meters, 200, receiving set, 311. 
Meters, 12,000, on 6,000 meter 

adjustment, 78. 
Meter, 15,000, coil receiver, 53. 
Method of switching for 

tuners, 338. 
Micro-farad, 97. 
Micro-henry, 99. 
Microphone amplifier, 274. 
Miles, power to transmit given 

distance, 91. 
Modulation, 238. 
Molybdenum, 258. 
Monotelephone, 276. 
Motor-generator, 105, 108, 348. 
Multi-layer receiving coils, 339. 
Multiple tuned antenna, 354. 



Multiple unit phase tuning, 
307. 

Multiplex radiophone, 243. 

Multiplex telephony, 244. 

Multiplier of generated fre- 
quency, 202. 

Multi-turn coil, 49. 

Multi-turn coil receiver, 27. 

Mutual inductance, 150. 

N 

Navy and Army radio appa- 
ratus, 244. 
Navy circuits, 307. 
Navy, loops used by, 52. 
Navy, under water antenna, 54. 
Navy wireless telephone, 245. 
Negative resistance, 219. 



Onde unique system, 204. 

One-quarter kilowatt set, 96. 

Operating room, 106. 

Operating rules, 378. 

Operation of a receiver, 293. 

Oscillation transformer, 153. 

Oscillations, 15, 172. 

Oscillations, function of con- 
denser, 135. 

Oscillations, graph of, 72. 

Oscillations in arc circuit, 190. 

Oscillations in quenched gap 
circuit, 105, 107. 

Oscillations, principles of, 182. 

Oscillations, production from 
audions, 235. 

Oscillations, production of, 68. 

Oscillations, production of 
various frequencies, 185. 

Outside grid tube, 218. 



Index 



387 



Patent discussion, 362, 372, 377. 

Patents, list, 362, 377. 

Percentage of coupling, 106. 

Pericon detector, 259. 

Phase modified receivers, 305. 

Phase rotator, 331. 

Phase shifting explained, 306. 

Phase tuning, 303, 306. 

Photographic recorder, 272. 

Piano, radio, 195. 

Plate circuit, 210. 

Plate current, 209. 

Pliotron, 217. 

Plural receiving sets, 345. 

Poles, 44, 45. 

Portable radio set, 240. 

Poulsen arc, 192. 

Poulsen "tipper," 273. 

Power for transmission, 92. 

Power for transmitter, 95. 

Power required for transmit- 
ter, 96. 

Primary and secondary wave 
lengths, 172. 

Primary circuit, 71. 

Progress of art, 379. 

Protection from lightning, 61. 

Protection from radio circuits, 
298. 

Protection of transmitting ap- 
paratus, 123. 



Quenched gap, 196. 

Quenched gap transmitter, 105, 

108. 
Quenched spark, advantages, 

197, 198. 



Quenched spark set, 187, 198. 
Quenched spark set, chart of, 
85. 



Radiant energy, 21. 
Radiation indicator, 170. 
Radiation, poor, 347. 
Radiation resistance, 36. 
Radio compass, 49, 52. 
Radio frequency amplifier, 217. 
Radio-Goniometer, 306. 
Radio information, advanced, 

148. 
Radio inspectors, 375. 
Radio on trains, 350. 
Radio patents, 362. 
Radiophones, 239. 
Radio sets, 374. 
Radio station list, 374. 
Radiotelephone, home-made, 

248. 
Radiotelephones, 238. See 

wireless telephone. 
Radiotelephone modulator, 244. 
Radiotelephone, simple, 189. 
Radiotelephone, portable, 240. 
Railroad wireless, 350. 
Range of sending station, 91. 
Reactance coil, 114. 
Reactance, transformer, 94. 
Received signal, 254. 
Received signals photographed, 

272. 
Receiver, a combination set, 

312. 
Receiver, automatic, 308. 
Receiver, for undamped waves> 

223. 



388 



Index 



Receiver, how it operates, 280. 

Receiver, ideal, 52. 

Receiver-recorder, 270. 

Receiver, sensitive recorder for 
signals, 273. 

Receiver, special circuits, 303. 

Receiver, telephone, 276. 

Receiver, testing a, 266, 268. 

Receiver, tuning of, 171. 

Receiver, with adjustable grid 
potential, 233. 

Receiver with sensitizer, 234. 

Receiving apparatus, 310, 314. 

Receiving apparatus for long 
waves, 340. 

Receiving circuits, 207, 252. 

Receiving condensers, 314. 

Receiving diagrams, 290. 

Receiving set, an ideal, 284. 

Receiving sets, plural, 345. 

Receiving station, 251. 

Receiving transformer, 332. 

Receiving transformer, im- 
proved, 344. 

Receiving tuners, 338. 

Receivers, phase modified, 305. 

Rectifier, 220, 252. 

Regenerative amplifier, 220. 

Repeater, 220. 

Resistance coupled amplifier, 
220. 

Resistance coupling, 220. 

Resistance, effect of in radio 
circuits, 73. 

Resistance, effect of in re- 
ceiver, 289. 

Resistance, in transmitter cir- 
cuits, 79. 

Resistance leak for vacuum 
tube, 220. 



Resonance, 65. 

Resonance, circuit relations, 69. 
Resonance, harmonic effect, 77. 
Resonance, principles of, 72, 

73. 
Roger's underground antenna, 

54. 
Rotary gap, 161. 
Rotary gap circuits, 166. 
Rotary quenched gap, 166. 
Rotary quenched gas gap, 167. 
Rules for operating, 377. 



Safety gap for transmitter, 105, 
107. 

Secondaries, construction of, 
114. 

Secondary wave length, 172. 

Section winder, 114. 

Selective receiving circuits, 294. 

Self modulated transmitter, 
236. 

Sending-receiving switch, 126. 

Sending station, 67. 

Sensitive receiver, 234. 

Sensitivity of detectors, 256. 

Series gap, 159. 

Set, one-quarter kilowatt, 96. 

Sharp tuned transmitter, 85. 

Sharp tuning, 80. 

Shields, 299. 

Ship's antenna capacity varies, 
103. 

Shock excitation, 168. 

Short wave oscillating receiver, 
311. 

Short wave receiver, 228. 

Short wave repeating ampli- 
fier, 228. 



Index 



389 



Shunt audibility meter, 281. 
Shunt resistance for measure- 
ments, 172. 
Shunt resonator construction, 

179. 
Signal, measuring strength of, 

281. 
Signals photographed, 273. 
Silicon, 258. 
Singing arc, 191. 
Simple wireless telephone, 246. 
Sliders, 329. 

Small local transmitter, 268. 
So-called "one wave" system, 

205. 
Solid rectifiers, 257. 
Spark coil construction, 115, 

117. 
Spark coils, condensers for, 98. 
Spark coils, tables for, 118. 
Spark gaps, 102, 105, 158. 
Spark rate, advantage of high, 

166. 
Spark transmitter, 91. 
Special receiving sets, 300. 
Static frequency transformer, 

203. 
Stations, cost of, 90. 
Storage battery, 131. 
Storage battery auxiliary, 105, 

107. 
Stray mitigator, 301, 303. 
Strays, cut down by resistance, 

289. 
Strays, effect of weather on, 

18. 
Strays, mitigation of, 54, 307. 
Strays, phase tuning of, 303. 
Strays, reduced number on 
coil receiver, 49, 50. 



Sub-surface radio, 52. 
Supports, aerial, 41. 
Sustained wave apparatus, 203. 
Sustained waves, production of, 

188. 
Switch, aerial, 126. 
Switch, ground, 62, 63. 



T aerial, 34. 

Telemechanics, 355. 

Telephone head set, 276. 

Telephone receiver, 252. 

Telephone receiver, head set 
resistance, 279. 

Tens and units switching, 338. 

Tests of receiver, 266. 

Thermo-couple, use of, 186. 

"Tickler" oscillating circuit, 
229. 

"Tikker," 273. 

Time and weather signals, 357. 

Time signal receiver, 300. 

Tone circuit, 168, 195. 

Tower, lattice, 45. 

Transcontinental wireless tele- 
phone, 241. 

Transformer, action of, 68. 

Transformer, adjustable, 111. 

Transformer, building a, 114. 

Transformer construction, 109. 

Transformer data, 110. 

Transformer, oscillation, con- 
struction, 153. 

Transformer preferred to 
spark coil, 119. 

Transformers, types, 92. 

Transmission, best at night, 18. 

Transmission, direction of, 16. 



390 



Index 



Transmission, distance of, 16. 

Transmission, range of, 91. 

Transmission, theory, 12. 

Transmission via sustained 
waves, 188. 

Transmission, wireless, 11. 

Transmitter, 65. 

Transmitter, alternator for, 
202. 

Transmitter, Edelman, 169. 

Transmitter, example of com- 
plete, 105, 108. 

Transmitter, inductively 
coupled, 67. 

Transmitter, principles of cir- 
cuit, 78. 

Transmitter, rotary gap, 167. 

Transmitter, self modulated, 
236. 

Transmitter, size for, 108. 

Transmitter, untuned, 82. 

Transmitting circuit, 66. 

Trouble finding, 346. 

Tube radio telephones, 238. 
See Vacuum tubes. 

Tuners, 326. 

Tuning, 20, 173, 255, 283. 

Tuning, automatic generator, 
236. 

Tuning, effect of beats, 80, 81. 

Tuning, illustrated, 83. 

Tuning long and short waves, 
293. 

Tuning methods, 284, 287. 

Tuning of a transmitter, 78. 

Tuning, phase changing 
method, 303. 

Tuning the receiver, 288. 

Tuning with a loose coupler, 
292. 



Two-tone transmitter, 169. 
Two transmitted waves, 83. 
Two wave lengths emitted, 288. 



U 



Ultra-audion, 223. 

Undamped and damped waves, 

287. 
Undamped wave generator, 

225. 
Undamped wave sets, 203. 
Undamped wave transmitter, 

188. 
Undamped waves, gap for, 168. 
Underground wireless, 52. 
Underwater radio, 52. 
Uni-control receiver, 308. 
Universal detector, 260. 
Universal wave receiver, 312. 
U. S. Patents, 362. 



Vacuum tube, aeroplane set, 
242. 

Vacuum tube circuit adjust- 
ments, 227. 

Vacuum tube circuits, 220. 

Vacuum tube, coil receiver, 53. 

Vacuum tube, curves of action, 
210. 

Vacuum tube, filament, 211. 

Vacuum tube generator, 237. 

Vacuum tube, grid potential 
adjustment, 233. 

Vacuum tube, high power, 239, 
247. 

Vacuum tube measurements, 
185. 



Index 



391 



Vacuum tube methods, 205, 
207. 

Vacuum tube modulation, 238. 

Vacuum tube, multiple circuits, 
241. 

Vacuum tube, one kilowatt, 
239, 247. 

Vacuum tube, operating char- 
acteristic, 209. 

Vacuum tube, operation, 210. 

Vacuum tube, principles of, 
208. 

Vacuum tube, self cooled, 247. 

Vacuum tube, special circuits, 
312. 

Vacuum tube transmitter, 
range of, 91. 

Vacuum tube with outside 
grid, 218. 

Vacuum tubes, plural bulb cir- 
cuits, 217, 220. 

Vacuum valve circuits, 207. 

Valve, see Vacuum tube, 213. 
214. 

Variable condenser, 318. 

Variometer, 331. 

Vibrator, spark coil, 119. 

Voltage, transformer, 95, 97. 

W 

Wave adjustments, 284. 
Wave changing, 169, 206. 
Wave length and group fre- 
quency change, 169. 
Wave length, calculation, 99. 



Wave length, change of, 70. 

Wave length, charts, 83, 84, 85. 

Wave length, effect of induct- 
ance and capacity, 74. 

Wave lengths in use, 18. 

Wave length, natural, 10. 

Wave length of aerials, 35, 36. 

Wave length, relation to fre- 
quency, 182. 

Wave lengths, short used, 25. 

Wavemeter, decrement deter- 
mination, 183. 

Wavemeter, heterodyne, 185. 

Wavemeter, self oscillating, 
185. 

Wavemeter, use of, 171. 

Wave train, decrement of, 183. 

Waves, absorption of, 17. 

Waves, electromagnetic, 23. 

Waves, generator for un- 
damped, 225. 

Waves in transmitting circuits, 
105, 107, 108. 

Waves, measurement of, 171. 

Waves, nature of, 24. 

Waves, produced by arc gen- 
erator, 191. 

Waves, radiation of, 11, 12. 

Waves, receiver for all kinds 
of, 312. 

Waves, special system, 200. 

Waves, untuned circuit for, 
83. 

Waves, velocity of, 15. 

Weather and time signals, 357. 

Weather reports, 358. 



392 



Index 



"Wired" wireless, 243. Wireless 

Wire, sizes for transformer, Wireless 

110. Wireless 
Wireless codes, 380. 239. 

Wireless compass, 352. Wireless 
Wireless for forest protection, 248. 

350. Wireless 
Wireless law, 25. 241. 

Wireless, multiplex system, Wireless 

243. lamp 

Wireless operated median— Wireless 

isms, 355. Wireless 
Wireless patents, 362. 13. 



piano, 195. 
progress, 379. 
telephone, 188, 236, 

telephone, a simple, 

telephone, high power, 

telephone operated on 
socket, 246. 
transmitter, 67. 
waves through earth, 



LATEST 

REVISED 

CATALOGUE 

of the Best 

Practical and Mechanical Books 

Including Automobile and Aviation Books 




PRACTICAL BOOKS FOR PRACTICAL MEN 

Each Book in this Catalogue is written by an 
Expert and is written so you can understand it 



PUBLISHED BY 

The Norman W. Henley Publishing Co. 

2 West 45th Street, New York, U. S. A. 

Established 1890 
2HF"" Any Book in this Catalogue sent prepaid on receipt of price 

Manuscripts solicited on Practical Subjects 



INDEX 



Abrasives and Abrasive Wheels 29 

Accidents 25 

Air Brakes 24, 26 

Arithmetic 13, 27, 37 

Automobile Books 3, 4, 5, 6 

Automobile Charts 6, 7 

Automobile Ignition Systems 7 

Automobile Lighting 4 

Automobile Questions and Answers. ... 5 

Automobile Repairing , . . . . 5 

Automobile Starting Systems 4 

Automobile Trouble Charts 6, 7 

Automobile Welding 6 

Aviation 8 

Bells, Electric 14 

Bevel Gear 21 

Boats, Motor 30 

Boiler Room Chart 9 

Boilers, Marine 30 

Brazing 9 

Cams 21 

Carburetion Trouble Charts 7 

Carburetors 4 

Car Charts 9 

Cements 12 

Change Gear 21 

Charts 6, 7, 9 

Chemistry 10 

Coal 24 

Combustion 19 

Concrete 10, 11, 12 

Concrete for Farm Use 11 

Concrete for Shop Use 11 

Cosmetics 32 

Dictionary 12, 17 

Dies 12 

Drawing 13, 32 

Drawing for Plumbers 32 

Dynamo Building 14 

Electric Bells 14 

Electric Dictionary 17 

Electric Switchboards 15 

Electric Toy Making 16 

Electric Wiring 15 

Electricity 13, 14, 15. 16, 17, 18 

Electroplating 19 

Encyclopedia 29 

Engine, Aviation 8 

E-T Air Brake 26 

Factory Management 19 

Ford Automobile 4 

Ford Tractor 4 

Ford Trouble Chart 7 

Formulas and Recipes 34 

Fuel 19 

Gas Engines 20, 21 

Gas Tractor 39 

Gearing and Cams 21 

Glossary Aviation Terms 8 

Heating 37 

High Frequency Apparatus 15 

Horse-Power Chart 36 

Hot Water Heating 37 

House Wiring 17, 18 

Hydraulics 22 

Ice 22 

Ignition Systems 4 

Ignition Trouble Chart 7 

India Rubber 35 

Interchangeable Manufacturing 27 

Inventions 22 

Kerosene Carburetors 4 

Knots 23 



Lathe Work 23 

Link Motions 24 

Liquid Air 24 

Locomotive Boilers 25 

Locomotive Breakdowns 25 

Locomotive Engineering 24, 25, 26 

Machinist Books 27, 28, 29 

Manual Training > 30 

Marine Engineering 30 

Marine Gasoline Engines 21 

Mechanical Drawing 13 

Mechanical Movements 28 

Metal Work 12 

Model Making 29 

Motor Boats 30 

Motorcycles 7,31 

Motor Truck 

Naval Engineering 30 

Patents 22 

Pattern Making 31 

Perfumery 32 

Perspective 13 

Plumbing 32, 33 

Punches 12 

Producer Gas 21 

Questions and Answers on Automobile . 

Questions on Heating 38 

Radio Time Signal Receiver 16, 17 

Railroad Accidents 25 

Railroad Charts . 

Recipe Book 34 

Refrigeration 22 

Repairing Automobiles. 

Rope Work 23 

Rubber 35 

Rubber Stamps 35 

Saw Filing 35 

Saws, Management of 35 

Screw Cutting 35 

Shipbuilders' Pocket Book 30 

Shop Construction 27 

Shop Management 27 

Shop Practice 27, 28, 29 

Shop Tools 29 

Sketching Paper 1 

Slide Valve 24 

Soldering 

Splices and Rope Work 23 

Steam Engineering 35, 36, 37 

Steam Heating 37 

Steel 38 

Storage Batteries 18 

Submarine Chart 

Switchboards 15 

Tapers 23 

Telegraphy, Wireless 14, 16, 18 

Telephone 18 

Thread-Cutting 27 

Tool Making 27 

Tool Steel 38 

Toy Making 1 

Tractive Power Chart 

Tractor, Gas 39 

Train Rules 2i 

Vacuum Heating 3: 

Valve Setting 2- 

Ventilation 37 

Walschaert Valve Gear 2 

Waterproofing 1 

Welding 6, 3 

Wireless Telegraphy 14, 16, 1 

Wiring 15, 17, 1 



Wiring Diagrams 1* 

Any of these books promptly sent prepaid to any address in the world on receipt of price. 
HOW TO REMIT.— By Postal Mo»er Order. Express Money Order. Bank Draft- or Registered Letter. 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



AUTOMOBILES 

THE MODERN GASOLINE AUTOMOBILE— ITS DESIGN, CONSTRUC- 
TION, MAINTENANCE AND REPAIR. By Victor W. Page, M.E. 
The latest and most complete treatise on the Gasoline Automobile ever issued. Written 
in simple language by a recognized authority, familiar with every branch of the auto- 
mobile industry. Free from technical terms. Everything is explained so simply 
that anyone of average intelligence may gain a comprehensive knowledge of the 
gasoline automobile. The information is up-to-date and includes, in addition to an 
exposition of principles of construction and description of all types of automobiles and 
their components, valuable money-saving hints on the care and operation of motor- 
cars propelled by internal combustion engines. Among some of the subjects treated 
might be mentioned: Torpedo and other symmetrical body forms designed to reduce 
air resistance; sleeve valve, rotary valve and other types of silent motors; increasing 
tendency to favor worm-gear power -transmission: universal application of magneto 
ignition: development of automobile electric-lighting systems; block motors; under- 
slung chassis; application of practical self-starters; long stroke and offset cylinder 
motors; latest automatic lubrication systems; silent chains for \alve operation and 
change-speed gearing; the use of front wheel brakes and many other detail refinements. 
By a careful study of the pages of this book one can gain practical knowledge of auto- 
mobile construction that will save time, money and worry. The book tells you just 
what to do, how and when to do it. Nothing has been omitted, no detail has been 
slighted. Every part of the automobile, its equipment, accessories, tools, supplies, 
spare parts necessary, etc., have been discussed comprehensively. If you are or 
intend to become a motorist, or are in any way interested in the modern Gasoline 
Automobile, this is a book you cannot afford to be without. 1032 pages — and 
more than 1,000 new and specially made detail illustrations, as well as many full-page 
and double-page plates, showing all parts of the automobile. Including 12 large 
folding plates. New Edition. Price $4.00 

WHAT IS SAID OP THIS BOOK: 

."It is the best book on the Automobile seen up to date." — J. H. Pile, Associate Editor 

Automobile Trade Journal. 

"Every Automobile Owner has use for a book of this character." — The Tradesman. 

"This book is superior to any treatise heretofore published on the subject." — The 

Inventive Age. 

"We know of no other volume that is so complete in all its departments, and in which 

the wide field of automobile construction with its mechanical intricacies is so plainly 

handled, both in the text and in the matter of illustrations." — The Motorist. 

"The book is very thorough, a careful examination failing to disclose any point in 

connection with the automobile, its care and repair, to have been overlooked." — 

Iron Age. 

"Mr. Page has done a great work, and benefit to the Automobile Field." — W. O. 

Hasford, Mgr. Y. M. C. A. Automobile School, Boston, Mass. 

" It is just the kind of a book a motorist needs if he wants to understand his car."— 

American Thresherman. 

THE MODERN MOTOR TRUCK, ITS DESIGN, CONSTRUCTION, OPERA- 
TION AND REPAIR. By Victor W. Page. 

Just off the press and treats on all types of motor trucks and industrial tractors and 
trailers. It considers all types of trucks, gasoline and electric, and all varieties of 
truck bodies. This book is written in language everyone can understand and is 
not in any sense of the word a technical treatise. It is a practical volume that will 
make special appeal to the truck driver who seeks to better his position and to the 
mechanic charged with the repair and upkeep of trucks. The factory or business 
executive who wants to obtain a complete working knowledge of truck operation 
problems will find this book a reference work of great value. The truck salesman or 
automobile dealer will find that this work contains information that means money 
to them. All garage and service station men should have a copy of this book for 
reference because truck construction differs from passenger car design in many im- 
portant respects. Anyone who reads this book is in touch with all the practical 
features that have been tested out in real service. 1921 Edition. Cloth, 6x9, 
962 pages, 750 illustrations Price $5.00 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

THE MODEL T FORD CAR, ITS CONSTRUCTION, OPERATION AND 
REPAIR, INCLUDING THE FORDSON FARM TRACTOR, F. A. LIGHT- 
ING AND STARTING SYSTEM, FORD MOTOR TRUCK. By Victor 
W. Page. 

This is the most complete and practical instruction book ever published on the Ford 
car and Fordson tractor. All parts of the Ford Model T car and Fordson tractor 
are described and illustrated in a comprehensive manner. The construction is 
fully treated and operating principle made clear to everyone. Complete instructions 
for driving and repairing are given. To the New Revised Edition matter has been 
added on the Ford Truck and Tractor Conversion Sets and Genuine Fordson Tractor. 
All parts are described. All repair processes illustrated and fully explained. Written 
so all can understand — no theory, no guesswork. New revised and enlarged Edition 
just published. 153 illustrations, 410 pages, 2 large folding plates. Price . $2.00 

AUTOMOBILE STARTING, LIGHTING AND IGNITION SYSTEMS. By 
Victor W. Page, M.E. . * 

This practical volume has been written with special reference to the requirements of the 
non-technical reader desiring easily understood, explanatory matter, relating to all 
types of automobile ignition, starting and lighting systems. It can be understood by 
anyone, even without electrical knowledge, because elementary electrical principles are 
considered before any attempt is made to discuss features of the various systems. 
These basic principles are clearly stated and illustrated with simple diagrams. All the 
leading systems of starting, lighting and ignition have been described and illustrated with 
the co-operation of the experts employed by the manufacturers. Wiring diagrams are 
shown in both technical and non-technical forms. All symbols are fully explained. It 
is a comprehensive review of modern starting and ignition system practice, and includes 
a complete exposition of storage battery construction, care and repair. All types of 
starting motors, generators, magnetos, and all ignition or lighting system units are 
fully explained. The systems of cars already in use as well as those that are to come 
are considered. Every person in the automobile business needs this volume. 5Mx7^. 
Cloth. 815 pages, 492 illustrations, 3 folding plates. New revised and enlarged 
edition. Price $3.00 

GASOLINE AND KEROSENE CARBURETORS, CONSTRUCTION, IN- 
STALLATION AND ADJUSTMENT. By Victor W. Page. A new up- 
to-date Book on Modern Carburetion Practice. 

This is a simple, comprehensive, and authoritative treatise for practical men ex- 
plaining all basic principles pertaining to carburetion, showing how liquid fuels are 
vaporized and turned into gas for operating all types of internal combustion engines in- 
tended to operate on vapors of gasoline, kerosene, benzol, and alcohol. All leading types 
of carburetors are described in detail, special attention being given to the forms devised 
to use the cheaper fuels such as kerosene. Carburetion troubles, fuel system troubles, 
carburetor repairs and installation, electric primers and economizers, hot spot mani- 
folds and all modern carburetor developments are considered in a thorough manner. 
Methods of adjusting all types of carburetors are fully discussed as well as sugges- 
tions for securing maximum fuel economy and obtaining highest engine power. 
This book is invaluable to repairmen, students, and motorists, as it includes the 
most complete exposition on kerosene carburetors ever published. The drawings 
showing carburetor construction are made from accurate engineering designs and 
show all parts of late types of carburetors. 213 pages. 89 illustrations. . $2.00 

HINTS AND TIPS FOR AUTOMOBILISTS. By Victor W. Page. 

The book is ideal for the busy man or woman who wants to know about car operation 
and upkeep because of the economies possible when an automobile is intelligently 
operated. It contains many money-saving hints and a brief simple exposition of 
location and remedy of roadside troubles apt to occur under ordinary operating 
conditions. Price 75 cents 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

AUTOMOBILE REPAIRING MADE EASY. By Victor W. Page, M.E. 
A comprehensive, practical exposition of every phase of modern automobile repairing 
practice. Outlines every process incidental to motor car restoration. Gives plans for 
workshop construction, suggestions for equipment, power needed, machinery and tools 
necessary to carry on the business successfully. Tells how to overhaul and repair all 
parts of all automobiles. Everything is explained so simply that motorists and students 
can acquire a full working knowledge of automobile repairing. This work starts with 
the engine, then considers carburetion, ignition, cooling and lubrication systems. The 
clutch, change-speed gearing and transmission system are considered in detail. Contains 
instructions for repairing all types of axles, steering gears and other chassis parts. 
Many tables, short cuts in figuring and rules of practice are given for the mechanic. 
Explains fully valve and magneto timing, "tuning" engines, systematic location of 
trouble, repair of ball and roller bearings, shop kinks, first aid to injured and a multi- 
tude of subjects of interest to all in the garage and repair business. 
This book contains special instructions on electric starting, lighting and ignition systems, 
tire repairing and rebuilding, autogenous welding, brazing and soldering, heat treatment of 
steel, latest timing practice, eight and twelve-cylinder motors, etc. 5%x8. Cloth. 1060 
pages, 1,000 illust rations, 11 folding plates. Price $4.00 

WHAT IS SAID OP THIS BOOK : 

" 'Automobile Repairing Made Easy ' is the best book on the subject I have ever seen 
and the only book I ever saw that is of any value in a garage." — Fred Jeffrey, Martins- 
burg, Neb. 

"I wish to thank you for sending me a copy of 'Automobile Repairing Made Easy.' I 
do not think it could be excelled." — S. W. Gisriel, Director of Instruction, Y. M. C. A., 
Philadelphia, Pa. 

QUESTIONS AND ANSWERS RELATING TO MODERN AUTOMOBILE 
CONSTRUCTION, DRIVING AND REPAIR. By Victor W. Page, M.E. 

A practical self-instructor for students, mechanics and motorists, consisting of thirty- 
seven lessons in the form of questions and answers, written with special reference to the 
requirements of the non-technical reader desiring easily understood, explanatory 
matter relating to all branches of automobiling. The subject-matter is absolutely 
correct and explained in simple language. If you can't answer all of the following 
questions, you need this work. The answers to these and nearly 2000 more are to 
be found in its pages. Give the name of all important parts of an automobile and 
describe their functions? Describe action of latest types of kerosene carburetors? 
What is the difference between a "double" ignition system and a "dual" ignition 
system? Name parts of an induction coil? How are valves timed? What is an 
electric motor starter and how does it work? What are advantages of worm drive 
gearing? Name all important types of ball and roller bearings? What is a "three- 
quarter" floating axle? What is a two-speed axle? What is the Vulcan electric gear 
shift? Name the causes of lost power in automobiles? Describe all noises due to 
deranged mechanism and give causes? How can you adjust a carburetor by the 
color of the exhaust gases? What causes "popping" in the carburetor? What tools 
and supplies are needed to equip a car? How do you drive various makes of cars? 
What is a differential lock and where is it used? Name different systems of wire 
wheel construction, etc. , etc. A popular work at a popular price. 5 34 x 7 y 2 . Cloth. 
701 pages, 387 illustrations, 3 folding plates. New revised edition. Price $2.50 

WHAT IS SAID OF THIS BOOK: 

"If you own a car — get this book." — The Glassworker. 

"Mr. Page has the faculty of making difficult subjects plain and understandable." — 
Bristol Press. 

"We can name no writer better qualified to prepare a book of instruction on auto- 
mobiles than Mr. Victor W. Page." — Scientific American. 
"The best automobile catechism that has appeared." — Automobile Topics. 
" There are few men, even with long experience, who will not find this book useful. 
Great pains have been taken to make it accurate. Special recommendation must be 
given to the illustrations, which have been made specially for the work. Such ex- 
cellent books as this greatly assist in fully understanding your automobile." — En- 
gineering News. 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



HOW TO RUN AN AUTOMOBILE. By Victor W. Page. 

This treatise gives concise instructions for starting and running all makes of gasoline 
automobiles, how to care for them, and gives distinctive features of control. De- 
scribes every step for shifting gears, controlling engine, etc. Among the chapters 
contained are: I. Automobile Parts and Their Functions. II. General Starting 
and Driving Instructions. III. Control Systems — Care of Automobiles. Thoroughly 
illustrated. 178 pages. 72 illustrations. Price $1.50 

THE AUTOMOBELIST'S POCKET COMPANION AND EXPENSE RECORD, 
By Victor W. Page. 

This book is not only valuable as a convenient cost record, but contains much in- 
formation of value to motorists. Includes a condensed digest of auto laws of all 
States, a lubrication schedule, hints for care of storage battery, and care of tires. 
location of road troubles, anti-freezing solutions, horse-power table, driving hints 
and many useful tables and recipes of interest to all motorists. Not a technical 
book in any sense of the word, just a collection of practical facts in simple language 
for the every-day motorist. Convenient pocket size. Price $1.50 

AUTOMOBILE WELDING WITH THE OXY-ACETYLENE FLAME. By 

M. Keith Dunham. 

Explains in a simple manner apparatus to be used, its care, and how to construct 
necessary shop equipment. Proceeds then to the actual welding of all automobile 
parts, in a manner understandable by everyone. Gives principles never to be for- 
gotten. This book is of utmost value, since the perplexing problems arising when 
metal is heated to a melting point are fully explained and the proper methods to 
overcome them shown. 167 pages. Fully illustrated. Price $1.50 



AUTOMOBILE, AVIATION AND MOTORCYCLE CHARTS 

AVIATION CHART— LOCATION OF AIRPLANE POWER PLANT TROUBLES 
MADE EASY. By Major Victor W. Page, A.S., S.C.U.S.R. 

A large chart outlining all parts of a typical airplane power plant, showing the points 
where trouble is apt to occur and suggesting remedies for the common defects. In- 
tended especially for aviators and aviation mechanics on school and field duty. 
Price .35 cents 

CHART. GASOLINE ENGINE TROUBLES MADE EASY— A CHART SHOW- 
ING SECTIONAL VIEW OF GASOLINE ENGINE. Compiled by Victor 
W. Page, M.E. 

It shows clearly all parts of a typical four-cylinder gasoline engine of the four-cycle 
type. It outlines distinctly all parts liable to give trouble and also details the de- 
rangements apt to interfere with smooth engine operation. 

Valuable to students, motorists, mechanics, repairmen, garagemen, automobile sales- 
men, chauffeurs, motorboat owners, motor-truck and tractor drivers, aviators, motor- 
cyclists, and all others who have to do with gasoline power plants. 
It simplifies location of all engine troubles, and while it will prove invaluable to the 
novice, it can be used to advantage by the more expert. It should be on the walls of 
every public and private garage, automobile repair shop, club house or school. It can 
be carried in the automobile or pocket with ease, and will insure against loss of time 
when engine trouble manifests itself. 

This sectional view of engine is a complete review of all motor troubles. It is prepared 
by a practical motorist for all who motor. More information for the money than ever 
before offered. No details omitted. Size 25x38 inches. Securely mailed on receipt 
of 35 cents 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

CHART. LOCATION OF FORD ENGINE TROUBLES MADE EASY. Com- 
piled by Victor W. Page, M.E. 

This shows clear sectional views depicting all portions of the Ford power plant and 
auxiliary groups. It outlines clearly all parts of the engine, fuel supply s3 T stem, igni- 
tion group and cooling system, that are apt to give trouble, detailing all derangements 
that are liable to make an engine lose power, start hard or work irregularly. This 
chart is valuable to students, owners, and drivers, as it simplifies location of all engine 
faults. Of great advantage as an instructor for the novice, it can be used equally well 
by the more expert as a work of reference and review. It can be carried in the tool- 
box or pocket with ease and will save its cost in labor eliminated the first time engine 
trouble manifests itself. Prepared with special reference to the average man's needs 
and is a practical review of aU motor troubles because it is based on the actual ex- 
perience of an automobile engineer-mechanic with the mechanism the chart describes. 
It enables the non-technical owner or operator of a Ford car to locate engine de- 
rangements by systematic search, guided by easily recognized symptoms instead of by 
guesswork. It makes the average owner independent of the roadside repair shop 
when touring. Must be seen to be appreciated. Size 25x38 inches. Printed on 
heavy bond paper. Price 35 cents 

CHART. LUBRICATION OF THE MOTOR CAR CHASSIS. Compiled by 
Victor W. Page, M.E. 

This chart presents the plan view of a typical six-cylinder chassis of standard design 
and all parts are clearly indicated that demand oil, also the frequency with which they 
must be lubricated and the kind of oil to use. A practical chart for all interested in 
motor-car maintenance. Size 24x38 inches. Price 35 cents 

CHART. LOCATION OF CARBURETION TROUBLES MADE EASY. Com- 
piled by Victor W. Page, M.E. 

This chart shows all parts of a typical pressure feed fuel supply system and gives 
causes of trouble, how to locate defects and means of remedying them. Size 24x38 
Price 35 cents 



CHART. LOCATION OF IGNITION SYSTEM TROUBLES MADE EASY. 

Compiled by Victor W. Page, M.E. 

In this diagram all parts of a typical double ignition system using battery and magneto 
current are shown, and suggestions are given for readily finding ignition troubles and 
eliminating them when found. Size 24x38 inches. Price 35 cents 

CHART. LOCATION OF COOLING AND LUBRICATION SYSTEM FAULTS. 
Compiled by Victob W. Page, M.E. 

This composite diagram shows a typical automobile power plant using pump circulated 
water-cooling system and the most popular lubrication method. Gives suggestions 
for curing all overhearing and loss of power faults due to faulty action of the oiling 
or cooling group. Size 24x38 inches. Price 35 cents 

CHART. LOCATION OF STARTING AND LIGHTING SYSTEM FAULTS. 

The most complete chart yet devised, showing all parts of the modern automobile 
starting, fighting and ignition systems, giving instructions for systematic location of 
all faults in wiring, lamps, motor or generator, switches and all other units. Invalu- 
able to motorists, chauffeurs and repairmen. Size 24x38 inches. Price . 35 cents 

CHART. MOTORCYCLE TROUBLES MADE EASY. Compiled by Victor 
W. Page, M.E. 

A chart showing sectional view of a single-cylinder gasoline engine. This chart 
simplifies location of all power-plant troubles. A single-cylinder motor is shown for 
simplicity. It outlines distinctly all parts liable to give trouble and also details the 
derangements apt to interfere with smooth engine operation. This chart wi?l prove 
of value to all who have to do with the operation, repair or sale of motorcycles. No 
details omitted. Size 30x20 inches. Price 35 cents 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



AVIATION 

A B C OF AVIATION. By Major Victor W. Page\ 

This book describes the basic principles of aviation, tells how a balloon or dirigible 
is made and why it floats in the air. Describes how an airplane flies. It shows in 
detail the different parts of an airplane, what they are and what they do. Describes 
all types of airplanes and how they differ in construction; as well as detailing the 
advantages and disadvantages of different types of aircraft. It includes a complete 
dictionary of aviation terms and clear drawings of leading airplanes. The reader 
will find simple instructions for unpacking, setting up, and rigging airplanes. A 
full description of airplane control principles is given and methods of flying are dis- 
cussed at length. 

This book answers every question one can ask about modern aircraft, their con- 
struction and operation. A self-educator on aviation without an equal. 274 pages. 
130 specially made illustrations with 7 plates. Price $2.50 

AVIATION ENGINES— DESIGN; CONSTRUCTION; REPAIR. By Major 



Victor W. Page, A.S., S.C.U.S.R. 



This treatise, written by a recognized authority on all of the practical aspects of 
internal combustion engine construction, maintenance, and repair, fills the need as 
no other book does. The matter is logically arranged; all descriptive matter is 
simply expressed and copiously illustrated, so that anyone can understand airplane 
engine operation and repair even if without previous mechanical training. This 
work is invaluable for anyone desiring to become an aviator or aviation mechanic. 
The latest rotary types, such as the Gnome Monosoupape, and LeRhone, are fully 
explained, as well as the recently developed Vee and radial types. The subjects 
of carburetion, ignition, cooling, and lubrication also are covered in a thorough manner. 
The chapters on repair and maintenance are distinctive and found in no other book 
on this subject. Not a technical book, but a practical, easily understood work of 
reference for all interested in aeronautical science. 589 pages. 253 illustrations. 
Price, net $3.00 

GLOSSARY OF AVIATION TERMS — ENGLISH-FRENCH; FRENCH- 
ENGLISH. By Major Victor W. Page, A.S., S.C.U.S.R., and Lieut. 
Paul Montariol, of the French Flying Corps. 

A complete glossary of practically all terms used in aviation, having lists in both 
French and English with equivalents in either language. Price, net . . $1.00 

APPLIED AERODYNAMICS. By G. P. Thompson. 

This is a scientific and mathematical treatise that has a special appeal to the student 
and engineer who are seeking exact information on the aerodynamics of neavier-than- 
air craft and data on airplane design testing. This book gives an up-to-date presen- 
tation of the existing state of Aeronautical Science. In addition to a very full dis- 
cussion of the qualities which determine the speed and rate of climb of an aeroplane 
and the method by which they can be calculated, special attention is paid to stability 
— a problem now fairly well understood, and to controllability — our knowledge of 
which is at present in a much more elementary state. Attention is directed to the 
numerous directions in which further information is required, especially in the form of 
full-scale experiments. 312 pages (7 x 10). Illustrated with over 142 Diagrams 
and Graphic Charts. Price $12.50 

AVIATION CHART— LOCATION OF AIRPLANE POWER PLANT TROUBLES 
MADE EASY. By Major Victor W. Page, A.S., S.C.U.S.R. 

A large chart outlining all parts of a typical airplane power plant, showing the points 
where trouble is apt to occur and suggesting remedies for the common defects. In- 
tended especially for aviators and aviation mechanics on school and field duty. 
Price 35 centf 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



BRAZING AND SOLDERING 

BRAZING AND SOLDERING. By James F. Hobart. 

The only book that shows you just how to handle any job of brazing or soldering that 
comes along : it tells you what mixture to use, how to make a furnace if you need one. 
Full of valuable kinks. The fifth edition of this book has just been published, and to 
it much new matter and a large number of tested formulae for all kinds of solders and 
fluxes have been added. IUustrated 35 cents 

SOLDERING AND BRAZING. By Raymond Francis Yates. 

This treatise gives all the necessary "kinks" that will enable one to accomplish suc- 
cessful soldering. If a mechanic has not succeeded in his soldering, this book may 
tell him just what he needs to produce good work — something that he may hereto- 
fore have forgotten. Price 75 cents 



CHARTS 

MODERN SUBMARINE CHART. 

A cross-section view, showing clearly and distinctly all the interior of a Submarine of 
the latest type. You get more information from this chart, about the construction and 
operation of a Submarine, than in any other way. No details omitted — everything 
is accurate and to scale. All the machinery and devices fitted in a modern Submarine 
Boat are shown 35 cents 

BOX CAR CHART. 

A chart showing the anatomy of a box car, having every part of the car numbered and 
its proper name given in a reference list 35 cent.*- 

GONDOLA CAR CHART. 

A chart showing the anatomy of a gondola car, having every part df the car numbered 
and its proper reference name given in a reference list . . 35 cents 

PASSENGER-CAR CHART. 

A chart showing the anatomy of a passenger-car, having every part of the car numbered 
and its proper name given in a reference list 35 cents 

STEEL HOPPER BOTTOM COAL CAR. 

A chart showing the anatomy of a steel Hopper Bottom Coal Car, having every part 
of the car numbered and its proper name given in a reference list 35 cents 

TRACTIVE POWER CHART. 

A chart whereby you can find the tractive power or drawbar pull of any locomotive 
without making a figure. Shows what cylinders are equal, how driving wheels and 
steam pressure affect the power. What sized engine you need to exert a given drawbar 
pull or anything you desire in this line 50 cents 

HORSE-POWER CHART 

Shows the horse-power of any stationary engine without calculation. No matter what 
the cylinder diameter of stroke, the steam pressure of cut-off, the revolutions, or 
whether condensing or non-condensing, it's all there. Easy to use, accurate, and 
saves time and calculations. Especially useful to engineers and designers. 50 cents 

BOILER ROOM CHART. By Geo. L. Fowler. 

A chart — size 14x28 inches — showing in isometric perspective the mechanisms be- 
longing in a modern boiler room. The various parts are shown broken or removed, 
so that the internal construction is fully illustrated. Each part is given a reference 
number, and these, with the corresponding name, are given in a glossary printed at 
the sides 35 cents 



9 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



CHEMISTRY 

HOW TO MAKE AND USE A SMALL CHEMICAL LABORATORY. By 

Raymond Francis Yates. 

The treatise covers all of the essentials of elementary chemistry. The law *f definite 
proportions, solutions, crystalloids, colloids, electrolysis, etc., are explained. The 
second part of the book is devoted to chemical and electro-chemical experiments. 
Only those experiments that will tend to broaden the reader's knowledge of chemistry 
in general have been chosen. Price 75 cents 



CONCRETE 

JUST PUBLISHED— CONCRETE WORKERS' REFERENCE BOOKS. A 
SERIES OF POPULAR HANDBOOKS FOR CONCRETE USERS. 

Prepared by A. A. Houghton. . . Each 75 cents 

The author, in preparing this Series, has not only treated on the usual types of construction, 
but explains and illustrates molds and systems that are not patented, but which are equal 
in value and often superior to those restricted by patents. These molds are very easily and 
cheaply constructed and embody simplicity, rapidity of operation, and the most successful 
results in the molded concrete. Each of these Twelve books is fully illustrated, and the 
subjects are exhaustively treated in plain English. 

CONCRETE WALL FORMS. By A. A. Houghton. 

A new automatic wall clamp is illustrated with working drawings. Other types of 

wall forms, clamps, separators, etc., are also illustrated and explained. 

(No. 1 of Series) 75 centl 

CONCRETE FLOORS AND SIDEWALKS. By A. A. Houghton. 

The molds for molding squares, hexagonal and many other styles of mosaic floor and 
sidewalk blocks are fully illustrated and explained. (No. 2 of Series) . .75 cents 

PRACTICAL CONCRETE SILO CONSTRUCTION. By A. A. Houghton. 

Complete working drawings and specifications are given for several styles of concrete 
silos, with illustrations of molds for monolithic and block silos. The tables, data, and 
information presented in this book are of the utmost value in planning and constructing 
all forms of concrete silos. (No. 3 of Series) . . . 75 cents 

MOLDING CONCRETE CHIMNEYS, SLATE AND ROOF TILES. By A. A. 

Houghton. 

The manufacture of all types of concrete slate and roof tile is fully treated. Valuable 
data on all forms of reinforced concrete roofs are contained within its pages. The 
construction of concrete chimneys by block and monolithic systems is fully illustrated 
and described. A number of ornamental designs of chimney construction with molds 
are shown in this valuable treatise. (No. 4 of Series.) ....... 75 cents 

MOLDING AND CURING ORNAMENTAL CONCRETE. By A. A. Houghton. 
The proper proportions of cement and aggregates for various finishes, also the method 
of thoroughly mixing and placing in the molds, are fully treated. An exhaustive 
treatise on this subject that every concrete worker will find of daily use and value 
(No. 5 of Series.) 75 cents 

CONCRETE MONUMENTS, MAUSOLEUMS^AND BURIAL VAULTS. By 

A. A. Houghton. 

The molding of concrete monuments to imitate the most expensive cut stone is ex- 
plained in this treatise, with working drawings of easily built molds. Cutting in- 
scriptions and designs are also fully treated. (No. 6 of Series.) ... 75 cents 

10 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

^ — — — — — ^— — — ^^^^-^— ■ — ^^^^— — ^— ^— 

MOLDING CONCRETE BATHTUBS, AQUARIUMS AND NATATORIUMS. 

By A. A. Houghton. 

Simple molds and instruction are given for molding many styles of concrete oathtubs. 
swimming-pools, etc. These molds are easily built and permit rapid and successful 
work. (No. 7 of Series.) 75 cents 

CONCRETE BRIDGES, CULVERTS AND SEWERS. By A. A. Houghton. 
A number of ornamental concrete bridges with illustrations of molds are given. A 
collapsible center or core for bridges, culverts and sewers is fully illustrated with de» 
tailed instructions for building. (No. 8 of Series.) 75 cents 

CONSTRUCTING CONCRETE PORCHES. By A- A. Houghton. 

A number of designs with working drawings of molds are fully explained so anyone 
can easily construct different styles of ornamental concrete porches without the pur- 
chase of expensive molds. (No. 9 of Series.) . 75 cents 

MOLDING CONCRETE FLOWER-POTS, BOXES, JARDINIERES, ETC. 
By A. A. Houghton. 

The molds for producing many original designs of flower-pots, urns, flower-boxes, 
jardinieres, etc., are fully illustrated and explained, so the worker can easily construct 
and operate same. (No. 10 of Series.) 75 cents 

MOLDING CONCRETE FOUNTAINS AND LAWN ORNAMENTS. By A. 
A. Houghton. 

The molding of a number of designs of lawn seats, curbing, hitching posts, pergolas, son 
dials and other forms of ornamental concrete for the ornamentation of lawns and gar- 
dens, is fully illustrated and described. (No. 11 of Series) 75 cents 

CONCRETE FROM SAND MOLDS. By A. A. Houghton. 

A Practical Work treating on a process which has heretofore been held as a trade secret 
by the few who possessed it, and which will successfully mold every and any class of 
ornamental concrete work. The process of molding concrete with sand molds is of 
the utmost practical value, possessing the manifold advantages of a low cost of molds, 
the ease and rapidity of operation, perfect details to all ornamental designs, density 
and increased strength of the concrete, perfect curing of the work without attention 
and the easy removal of the molds regardless of any undercutting the design may have. 
192 pages. Fully illustrated. Price $3.00 

ORNAMENTAL CONCRETE WITHOUT MOLDS. By A. A. Houghton. 

The process for making ornamental concrete without molds has long been held as a 
secret, and now, for the first time, this process is given to the public. The book 
reveals the secret and is the only book published which explains a simple, practical 
method whereby the concrete worker is enabled, by employing wood and metal tem- 
plates of different designs, to mold or model in concrete any Cornice, Archivolt, 
Column, Pedestal. Base Cap. Urn or Pier in a monolithic form — right upon the job. 
These may be molded in units or blocks, and then built up to suit the specifications 
demanded. This work is fully illustrated, with detailed engravings. Price . $2.00 

CONCRETE FOR THE FARM AND IN THE SHOP. By H. Colin 
Campbell, C.E., E.M. 

A new book illustrating and describing in plain, simple language many of the 
numerous applications of concrete within the range of the home worker. Among the 
subjects treated are: 

Principles of reinforcing ; methods of protecting concrete so as to insure proper harden- 
ing; home-made mixers; mixing by hand and machine; form construction, described 
and illustrated by drawings and photographs; construction of concrete walls and 
fences; concrete fence posts; concrete gate posts; corner posts; clothes line posts; 
grape arbor posts; tanks; troughs; cisterns; hog wallows; feeding floors and barn- 
yard pavements ; foundations ; well curbs and platforms ; indoor floors ; sidewalks ; steps ; 
concrete hotbeds and cold frames; concrete slab roofs; walls for buildings; repairing 
leaks in tanks and cisterns, etc., etc. A number of convenient and practical tables 
for estimating quantities, and some practical examples, are also given. (5 x 7). 
149 pages, 51 illustrations. Price $1.00 

II 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

POPULAR HANDBOOK FOR CEMENT AND CONCRETE USERS. By 

Myron H. Lewis. 

This is a concise treatise of the principles and methods employed in the manufacture 
and use of cement in all classes of modern works. The author has brought together 
in this work all the salient matter of interest to the user of concrete and its many 
diversified products. The matter is presented in logical and systematic order, clearly 
written, fully illustrated and free from involved mathematics. Everything of value to 
the concrete user is given, including kinds of cement employed in construction, concrete 
architecture, inspection and testing, waterproofing, coloring and painting, rules, tables, 
working and cost data. The book comprises thirty-three chapters, 430 pages, 126 
illustrations. Price $3.00 

WATERPROOFING CONCRETE. By Myron H. Lewis. 

Modern Methods of Waterproofing Concrete and Other Structures. A condensed 
statement of the Principles, Rules, and Precautions to be Observed in Waterproofing 
and Dampproofing Structures and Structural Materials. Price . . . . 75 cents 

DICTIONARIES 

STANDARD ELECTRICAL DICTIONARY. By T. O'Conor Sloane. 

An indispensable work to all interested in electrical science. Suitable alike for the 
student and professional. A practical handbook of reference containing definitions in 
about 5000 distinct words, terms and phrases. The definitions are terse and concise 
and include every term used in electrical science. Recently issued. An entirely new 
edition. Should be in the possession of all who desire to keep abreast with the progress 
of this branch of science. Complete, concise and convenient. Nearly 800 pages. Nearly 
500 illustrations. New Revised and Enlarged Edition. Price $5.00 

DIES— METAL WORK 

DIES: THEIR CONSTRUCTION AND USE FOR THE MODERN W0RE3NG 
OF SHEET METALS. By J. V. Woodworth. 

A most useful book, and one which should be in the hands of all engaged in the pres- 
working of metals; treating on the Designing, Constructing, and Use of Tools, Fixtures 
and Devices, together with the manner in which they should be used in the Power 
Press, for the cheap and rapid production of the great variety of sheet-metal articles 
now in use. It is designed as a guide to the production of sheet-metal parts at the 
minimum of cost with the maximum of output. The hardening and tempering of 
Press tools and the classes of work which may be produced to the best advantage by 
the use of dies in the power press are fully treated. Its 505 illustrations show dies, 
press fixtures and sheet-metal working devices, the descriptions of which are so clear and 
practical that all metal-working mechanics will be able to understand how to design, 
construct and use them. Many of the dies and press fixtures treated were either 
constructed by the author or under his supervision. Others were built by skilful - 
mechanics and are in use in large sheet-metal establishments and machine shops. 
6th Edition. 400 pages, 523 illustrations. Price $3.50 

PUNCHES, DIES AND TOOLS FOR MANUFACTURING IN PRESSES. By 
J. V. Woodworth. 

This work is a companion volume to the author's elementary work entitled "Dies, Their 
Construction and Use." It does not go into the details of die-making to the extent of 
the author's previous book, but gives a comprehensive review of the field of operations 
carried on by presses. A large part of the information given has been drawn from the 
author's personal experience. It might well be termed an Encyclopedia of Die-Making, 
Punch-Making, Die-Sinking, Sheet-Metal Working, and Making of Special Tools, Sub- 
presses, Devices and Mechanical Combinations for Punching, Cutting, Bending, Form- 
ing, Piercing, Drawing, Compressing and Assembling Sheet-Metal Parts, and also Arti- 
cles of other Materials in Machine Tools. 3rd Edition. 483 pages, 702 illustrations. 
Price , $4.50 

I? 



CATALOGUE OF GOoD, PRACTICAL BOOKS 



DRAWING— SKETCHING PAPER 

PRACTICAL PERSPECTIVE. By Richards and Colvin. 

Shows just how to make all kinds of mechanical drawings in the only practical per- 
spective isometric. Makes everything plain so that any mechanic can understand 
a sketch or drawing in this way. Saves time in the drawing room, and mistakes in the 
shops. Contains practical examples of various classes of work. 4th Edition. 75 cents 

LINEAR PERSPECTIVE SELF-TAUGHT. By Herman T. C. Kraus. 

This work gives the theory and practice of linear perspective, as used in architectural, 
engineering and mechanical drawings. Persons taking up the study of the subject 
by themselves will be able, by the use of the instruction given, to readily grasp the 
subject, and by reasonable practice become good perspective draftsmen. The arrange- 
ment of the book is good; the plate is on the left-hand, while the descriptive text 
follows on* the opposite page, so as to be readily referred to. The drawings are on 
sufficiently large scale to show the work clearly and are plainly figured. There is 
included a self-explanatory chart which gives all information necessary for the thorough 
understanding of perspective. This chart alone is worth many times over the price of 
the book. 2d Revised and enlarged Edition $3.00 

SELF-TAUGHT MECHANICAL DRAWING AND ELEMENTARY MACHINE 
DESIGN. By F. L. Sylvester, M.E., Draftsman, with additions by Erik 
Oberg, associate editor of "Machinery." 

This is a practical treatise on Mechanical Drawing and Machine Design, comprising 
the first principles of geometric and mechanical drawing, workshop mathematics, 
mechanics, strength of materials and the calculations and design of machine details. 
The author's aim has been to adapt this treatise to the requirements of the practical 
mechanic and young draftsman and to present the matter in as clear and concise a 
manner as possible. To meet the demands of this class of students, practically all the 
important elements of machine design have been dealt with, and in addition algebraic 
formulas have been explained, and the elements of trigonometry treated in the manner 
best suited to the needs of the practical man. The book is divided into 20 chapters, 
and in arranging the material, mechanical drawing, pure and simple, has been taken 
up first, as a thorough understanding of the principles of representing objects facilitates 
the further study of mechanical subjects. This is followed by the mathematics neces- 
sary for the solution of the problems in machine design which are presented later, and 
a practical introduction to theoretical mechanics and the strength of materials. The 
various elements entering into machine design, such as cams, gears, sprocket-wheels, 
cone pulleys, bolts, screws, couplings, clutches, shafting and fly-wheels, have been 
treated in such a way as to make possible the use of the work as a text-book for a 
continuous course of study. 333 pages, 218 engravings. Price. . . . $2.50 

A NEW SKETCHING PAPER. 

A new specially ruled paper to enable you to make sketches or drawings in isometric 
perspective without any figuring or fussing. It is being used for shop details as well 
as for assembly drawings, as it makes one sketch do the work of three, and no workman 
can help seeing just what is wanted. Pads of 40 sheets, 6x9 inches, 40 cents. Pads 
of 40 sheets, 9x12 inches, 75 cents; 40 sheets, 12x18, Price $1.50 



ELECTRICITY 

ARITHMETIC OF ELECTRICITY. By Prof. T. O'Conor Sloane. 

A practical treatise on electrical calculations of all kinds reduced to a series of rules, all 
of the simplest forms, and involving only ordinary arithmetic; each rule illustrated 
by one or more practical problems, with detailed solution of each one. This book is 
classed among the most useful works published on the science of electricity, covering 
as it does the mathematics of electricity in a manner that will attract the attention 
of those who are not familiar with algebraical formulas. 22nd Edition. 196 pages. 
Price $1.50 



13 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

COMMUTATOR CONSTRUCTION. By Wm. Baxter, Jr. 

The business end of any dynamo or motor of the direct current type is the commutator. 
This book goes into the designing, building, and maintenance of commutators, shows 
how to locate troubles and how to remedy them; everyone who fusses with dynamos 
needs this. 5th Edition 35 cents 

CONSTRUCTION OF A TRANSATLANTIC WIRELESS RECEIVING SET. 

By L. G. Pacent and T. S. Curtis. 

A work for the Radio student who desires to construct and operate apparatus that 
will permit of the reception of messages from the large stations in Europe with an 
aerial of amateur proportions. 36 pages. 23 illustrations, cloth. Price . 35 cents 

DYNAMO BUILDING FOR AMATEURS, OR HOW TO CONSTRUCT A 
FIFTY- WATT DYNAMO. By Arthur J. Weed, Member of N. Y. Electrical 

Society. 

A practical treatise showing in detail the construction of a small dynamo or motor, the 
entire machine work of which can be done on a small foot lathe. Dimensioned working 
drawings are given for each piece of machine work, and each operation is clearly 
described. This machine, when used as a dynamo, has an output of fifty watts; when 
used as a motor it will drive a small drill press or lathe. It can be used to drive a 
sewing machine on any and all ordinary work. The book is illustrated with more 
than sixty original engravings showing the actual construction of the different parts. 
Among the contents are chapters on: 1. Fifty- Watt Dynamo. 2. Side Bearing 
Rods. 3. Field Punching. 4. Bearings. 5. Commutator. 6. Pulley. 7. Brush 
Holders. 8. Connection Board. 9. Armature Shaft. 10. Armature. 11. Armature 
Winding. 12. Field Winding. 13. Connecting and Starting. Price, cloth, $1.00 

DESIGN DATA FOR RADIO TRANSMITTERS AND RECEIVERS. By 

Milton B. Sleeper. 

Far from being a collection of formulas, Design Data takes up in proper sequence the 
problems encountered in planning all types of receiving sets for short, medium and 
long wave work, and spark coil, transformer and vacuum tube transmitters operating 
on 200 meters. Tables have been worked out so that values can be found without 
the use of mathematics. Radio experimenters will find here information which will 
enable them to have the most modern and efficient equipment. Price . . 75 cents 

DYNAMOS AND ELECTRIC MOTORS AND ALL ABOUT THEM. By 

Edward Trevert. 

This volume gives practical directions for building a two H. P. Dynamo of the Edison 
type capable of lighting about fifty mazda lamps of the 20-watt size. In addition, it 
gives directions for building two small electric motors suitable for running sewing 
machines. The concluding chapter describes the construction of a simple bichromate 
battery adapted for running electric motors. 96 pages. Fully illustrated with detail 
drawings. Cloth.. Price $1.00 

ELECTRIC BELLS. By M. B. Sleeper. 

A complete treatise for the practical worker in installing, operating, and testing 
bell circuits, burglar alarms, thermostats, and other apparatus used with electric 
bells. Both the electrician and the experimenter will find in this book new material 
which is essential in their work. Tools, bells, batteries, unusual circuits, burglar 
alarms, annunciators, systems, thermostats, circuit breakers, time alarms, and other 
apparatus used in bell circuits are described from the standpoints of their applica- 
tion, construction, and repair. The detailed instructions for building the apparatus 
will appeal to the experimenter particularly. The practical worker will find the 
chapters on Wiring Calculation of Wire Sizes and Magnet Windings, Upkeep of 
Systems and the Location of Faults of the greatest value in their work. 124 pages. 
Fully illustrated. Price 73 cents 

H 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

EXPERIMENTAL HIGH FREQUENCY APPARATUS — HOW TO MAKE 
AND USE IT. By Thomas Stanley Curtis. 

This book tells you how to build simple high frequency coils for experimental purpose 
in the home, school laboratory, or on the small lecture platform. The book is really 
a supplement to the same author's " High Frequency Apparatus." The experimental 
side only is covered in this volume, which is intended for those who want to build 
small coils giving up to an eighteen-inch spark. The book contains valuable in- 
formation for the physics or the manual training teacher who is on the lookout for 
interesting projects for his boys to build or experiment with. The apparatus is 
simple, cheap and perfectly safe, and with it some truly startling experiments may be 
performed. Among the contents are: Induction Coil Outfits Operated on Battery 
Current. Kicking Coil Apparatus. One-Half Kilowatt Transformer Outfit. Parts 
and Materials, etc., etc. 69 pages. Illustrated. Price 50 cents 

HIGH FREQUENCY APPARATUS, ITS CONSTRUCTION AND PRACTICAL 
APPLICATION. By Thomas Stanley Curtis. 

The most comprehensive and thorough work on this interesting subject ever produced. 
The book is essentially practical in its treatment and it constitutes an accurate record 
of the researches of its author over a period of several years, during which time dozens 
of coils were built and experimented with. The work has been divided into six basic 
parts. The first two chapters teU the uninitiated reader what the high frequency 
current is, what it is used for, and how it is produced. The second section, comprising 
four chapters, describes in detail the principles of the transformer, condenser, spark 
gap, and oscillation transformer, and covers the main points in the design and con- 
struction of these devices as applied to the work in hand. The third section covers 
the construction of small high frequency outfits designed for experimental work in the 
home laboratory or in the classroom. The fourth section is devoted to electro- 
therapeutic and X-Ray apparatus. The fifth describes apparatus for the cultivation 
of plants and vegetables. The sixth section is devoted to a comprehensive discussion 
of apparatus of large size for use upon the stage in spectacular productions. The 
closing chapter, giving the current prices of the parts and materials required for the 
construction of the apparatus described, is included with a view to expediting the 
purchase of the necessary goods. The Second Edition includes much new matter 
along the line of home-made therapeutic outfits for physicians' use. The matter on 
electro plant culture has also been elaborated upon. Second Revised and Enlarged 
Edition. 266 pages. New second edition. Fully illustrated. Price . $3.00 

ELECTRIC WIRING, DIAGRAMS AND SWITCHBOARDS. By Newton 
Harrison. 

A thoroughly practical treatise covering the subject of Electric Wiring in all its branches, 
including explanations and diagrams which are thoroughly explicit and greatly simplify 
the subject. Practical, every-day problems in wiring are presented and the method 
of obtaining intelligent results clearly shown. Only arithmetic is used. Ohm's law 
is given a simple explanation with reference to wiring for direct and alternating 
currents. The fundamental principle of drop of potential in circuits is shown with its 
various applications. The simple circuit is developed with the position of mains, 
feeders and branches; their treatment as a part of a wiring plan and their employ- 
ment in house wiring clearly illustrated. Some simple facts about testing are included 
in connection with the wiring. Molding and conduit work are given careful considera- 
tion; and switchboards are sy sterna tically treated, built up and illustrated, showing 
the purpose they serve, for connection with the circuits, and to shunt and compound 
wound machines. The simple principles of switchboard construction, the develop- 
ment of the switchboard, the connections of the various instruments, including the 
lightning arrester, are also plainly set forth. 

Alternating current wiring is treated, with explanations of the power factor, conditions 
calling for various sizes of wire, and a simple way of obtaining the sizes for single-phase, 
two-phase and three-phase circuits. This is the only complete work issued showing 
and telling you what you should know about direct and alternating current wiring. It 
is a ready reference. The work is free from advanced technicalities and mathematics, 
arithmetic being used throughout. It is in every respect a handy, well- written, 
instructive, comprehensive volume on wiring for the wireman. foreman, contractor, 
or electrician. 3rd edition, revised and enlarged. 315 pages; 137 illustrations. 
Price $2.50 

is 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

ELECTRIC TOY MAKING, DYNAMO BUILDING, AND ELECTRIC MOTOR 
CONSTRUCTION. By Prof. T. O'Conor Sloane. 

This work treats of the making at home of electrical toys, electrical apparatus, motors, 
dynamos and instruments in general, and is designed to bring within the reach of 
young and old the manufacture of genuine and useful electrical appliances. The work 
is especially designed for amateurs and young folks. 

Thousands of our young people are daily experimenting, and busily engaged in making 
electrical toys and apparatus of various kinds. The present work is just what is want- 
ed to give the much needed information in a plain, practical manner, with illustrations 
to make easy the carrying out of the work. 20th Edition. 210 pages, 77 illustrations. 
Price $1.50 

ELECTRICIANS' HANDY BOOK. By Prof. T. O'Conor Sloane. 

This work is intended for the practical electrician who has to make things go. The 
entire field of electricity is covered within its pages. Among some of the subjects treated 
are: The Theory of the Electric Current and Circuit, Electro-Chemistry, Primary 
Batteries, Storage Batteries, Generation and Utilization of Electric Powers, Alter- 
nating Current, Armature Winding, Dynamos and Motors, Motor Generators, 
Operation of the Central Station Switchboards, Safety Appliances, Distribution 
of Electric Light and Power, Street Mains, Transformers, Arc and Incandescent 
Lighting, Electric Measurements, Photometry, Electric Railways, Telephony, Bell- 
Wiring, Electric-Plating, Electric Heating, Wireless Telegraphy, etc. It contains no 
useless theory; everything is to the point. It teaches you just what you want to 
know about electricity. It is the standard work published on the subject. Forty- 
six chapters, 600 engravings. New 5th Edition, Revised and Enlarged. Price $4.00 

ELECTRICITY SIMPLIFIED. By Prof. T. O'Conor Sloane. 

The object of "Electricity Simplified" is to make the subject as plain as possible and 
to show what the modern conception of electricity is; to show how two plates of 
different metal, immersed in acid, can send a message around the globe; to explain 
how a bundle of copper wire rotated by a steam engine can be the agent in lighting 
our streets, to tell what the volt, ohm and ampere are, and what high and low tension 
mean; and to answer the questions that perpetually arise in the mind in this age of 
electricity. 15th Revised Edition. 218 pages. Illustrated. Price . . $1.50 

EXPERIMENTAL WIRELESS STATIONS. By P. E. Edelman. 

The theory, design, construction and operation is fully treated including Wireless 
Telephony, Vacuum Tube, and quenched spark systems. The new enlarged edition 
is just issued and is strictly up to date, correct and complete. This book tells 
how to make apparatus to not only hear all telephoned and telegraphed radio mes- 
sages, but also how to make simple equipment that works for transmission over rea- 
sonably long distances. 1'hen there is a host of new information included. The 
first and only book to give you all the recent important radio improvements, some 
oi which have never before been published. This volume anticipates every need of 
the reader who wants the gist of the art, its principles, simplified calculations, appara- 
tus dimensions, and understandable directions for efficient operation. 
Vacuum tube circuits; amplifiers; long-distance sets; loop, coil, and underground 
receivers; tables of wave-lengths, capacity, inductance; such are a few of the sub- 
jects presented in detail that satisfies. It is independent and one of the few that 
describe all modern systems. 

Endorsed by foremost instructors for its clear accuracy, preferred by leading amateurs 
for its dependable designs. The new experimental Wireless Stations is sure 
to be most satisfactory for your purposes. 27 chapters, 392 pages. 167 illustra- 
tions. Price $3.00 

RADIO TIME SIGNAL RECEIVER. By Austin C. Lescarboura. 

This new book, "A Radio Time Signal Receiver," tells you how to build a simple 
outfit designed expressly for the beginner. You can build the outfits in your own 
workshop and install them for jewelers either on a one-payment or a rental basis. 
The apparatus is of such simple design that it may be made by the average amateur 
mechanic possessing a few ordinary tools. 42 pages. Paper. Price , . 35 cents 

16 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

HOUSE WIRING. By Thomas W. Poppe. 

This work describes and illustrates the actual installation of Electric Light Wiring, 
the manner in which the work should he done, and the method of doing it. The book 
can be conveniently carried in the pocket. It is intended for the Electrician, Helps, 
and Apprentice. It solves all Wiring Problems and contains nothing that conflicts 
with the rulings of the National Board of Fire Underwriters. It gives just the informa- 
tion essential to the Successful Wiring of a Building. Among the subjects treated are 
Locating the Meter. Panel Boards. Switches. Plug Receptacles. Brackets. Ceiling 
Fixtures. The Meter Connections. The Feed Wires. The Steel Armored Cable 
System. The Flexible Steel Conduit System. The Ridig Conduit System. A digest 
of the National Board of Fire Underwriters' rules relating to metallic wiring systems. 
Various switching arrangements explained and diagrammed. The easiest method or 
testing the Three- and Four-way circuits explained. The grounding of all metallic 
wiring systems and the reason for doing so shown and explained. The insulation of 
the metal parts of lamp fixtures and the reason for the same described and illustrated. 
208 pages. 4th Edition, revised and enlarged. 160 illustrations. Flexible cloth. 
Price $1.00 

HOW TO BECOME A SUCCESSFUL ELECTRICIAN. By Prof. T. O'Conor 
Sloane. 

Every young man who wishes to become a successful electrician should read this book. 
It tells in simple language the surest and easiest way to become a successful electrician. 
The studies to be followed, methods of work, field of operation and the requirement, 
of the successful electrician are pointed out and fully explained. Every young en- 
gineer will find this an excellent stepping stone to more advanced works on electricity 
which he must master before success can be attained. Many young men become dis- 
couraged at the very outstart by attempting to read and study books that are far 
beyond their comprehension. This book serves as the connecting link between the 
rudiments taught in the public schools and the real study of electricity. It is inter- 
esting from cover to cover. 19th Revised Edition, just issued. 205 pages. Illus- 
trated. Price $1.50 

RADIO HOOK-UPS. By Milton B. Sleeper. 

In this book the best circuits for different instruments and various purposes have been 
carefully selected and grouped together. All the best circuits for damped and un- 
damped wave receiving sets, buzzer, : spark coil and transformer sending equipment, as 
well as vacuum tube telegraph and telephone transmitters, wavemeters, vacuum tube 
measuring instruments, audibility meters, etc., are shown in this book. . 75 cents 

STANDARD ELECTRICAL DICTIONARY. By T. O'Conor Sloane. 

An indispensable work to all interested in electrical science. Suitable alike for the 
student and professional. A practical handbook of reference containing definitions 
of about 5,000 distinct words, terms and phrases. The definitions are terse and 
concise and include every term used in electrical science. Recently issued. An en- 
tirely new edition. Should be in the possession of all who desire to keep abreast with 
the progress of this branch of science. In its arrangement and typography the book 
is very convenient. The word or term defined is printed in black-faced type which 
readily catches the eye, while the body of the page is in smaller but distinct type. The 
definitions are well worded, and so as to be understood by the non-technical reader. 
The general plan seems to be to give an exact, concise definition, and then amplify 
and explain in a more popular way. Synonyms are also given, and references to other 
words and phrases are made. A very complete and accurate index of fifty pages is 
at the end of the volume; and as this index contains all synonyms, and as all phrases 
are indexed in every reasonable combination of words, reference to the proper place 
in the body of the book is readily made. It is difficult to decide how far a book of 
this character is to keep the dictionary form, and to what extent it may assume the 
encyclopedia form. For some purposes, concise, exactly worded definitions are needed ; 
for other purposes, more extended descriptions are required. This book seeks to satisfy 
both demands, and does it with considerable success. Complete, concise and con- 
venient. 800 pages. Nearly 500 illustrations. New Revised and Enlarged Edition. 
Price $5.00 

17 



CATALOGUE uF GOOD, PRACTICAL BOOKS 

STORAGE BATTERIES SIMPLIFIED. By Victor W. Page, M.S.A.E. 

A complete treatise on storage battery operating principles, repairs and applications 
The greatly increasing application of storage batteries in modern engineering and 
mechanical work has created a demand for a book that will consider this subject 
completely and exclusively. This is the most thorough and authoritative treatise 
ever published on this subject. It is written in easily understandable, non-technical 
language so that anyone may grasp the basic principles of storage battery action as 
well as their practical industrial applications. All electric and gasoline automobiles 
use storage batteries. Every automobile repairman, dealer or salesman should have a 
good knowledge of maintenance and repair of these important elements of the motor 
car mechanism. This book not only tells how to charge, care for and rebuild storage 
batteries but also outlines all the industrial uses. Learn how they run street cars, 
locomotives and factory trucks. Get an understanding of the important functions they 
perform in submarine boats, isolated lighting plants, railway switch and signal systems, 
marine applications, etc. This book tells how they are used in central station standby 
service, for starting automobile motors and in ignition systems. Every practical use 
of the modern storage battery is outlined in this treatise 208 pages. Fully illus- 
trated. Price $2.00 

TELEPHONE CONSTRUCTION, INSTALLATION, WIRING, OPERATION 

AND MAINTENANCE. By W. H. Radcliffe and H. G. Gushing. __. 

This book is intended for the amateur, the wireman, or the engineer who desires to 
establish a means of telephonic communication between the rooms of his home, office, 
or shop. It deals only with such things as may be of use to him rather than with 
theories. 

Gives the principles of construction and operation of both the Bell and Independent 
instruments ; approved methods of installing and wiring them ; the means of protecting 
them from lightning and abnormal currents; their connection together for operation 
as series or bridging stations ; and rules for their inspection and maintenance. Line 
wiring and the wiring and operation of special telephone systems are also treated. 
Intricate mathematics are avoided, and all apparatus, circuits and systems are thor- 
oughly described. The appendix contains definitions of units and terms used in the 
text. Selected wiring tables, which are very helpful, are also included. Among the 
subjects treated are Construction, Operation, and Installation of Telephone Instru- 
ments; Inspection and Maintenance of Telephone Instruments; Telephone Line 
Wiring; Testing Telephone Line Wires and Cables; Wiring and Operation of Special 
Telephone Systems, etc. 2nd Edition, revised and enlarged. 223 pages. 154 
illustrations , $1.50 

WIRELESS TELEGRAPHY AND TELEPHONY SIMPLY EXPLAINED. By 
Alfred P. Morgan. 

This is undoubtedly one of the most complete and comprehensible treatises on the' 
subject ever published, and a close study of its pages will enable one to master all the 
details of the wireless transmission of messages. The author has filled a long-felt 
want and has succeeded in furnishing a lucid, comprehensible explanation in simple 
language of the theory and practice of wireless telegraphy and telephony. 
Among the contents are: Introductory; Wireless Transmission and Eeception — The 
Aerial System, Earth Connections — The Transmitting Apparatus, Spark Coils and 
Transformers, Condensers, Helixes, Spark Gaps, Anchor Gaps, Aerial Switches — The 
Receiving Apparatus. Detectors, etc. — Tuning and Coupling, Tuning Coils, Loose 
Couplers, Variable Condensers, Directive Wave Systems — Miscellaneous Apparatus, 
Telephone Receivers, Range of Stations, Static Interference — Wireless Telephones, 
Sound and Sound Waves, The Vocal Cords and Ear — Wireless Telephone, How Sounds 
Are Changed into Electric Waves — Wireless Telephones, The Apparatus — Summary. 
154 pages. 156 engravings. Price $1.50 

WIRING A HOUSE. By Herbert Pratt. 

Shows a house already built; tells just how to start about wiring it; where to begin; 
what wire to use; how to run it according to Insurance Rules; in fact, just the informa- 
tion you need. Directions apply equally to a shop. Fourth edition ... . 35 cents 

18 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



ELECTROPLATING 

THE MODERN ELECTROPLATER. By Kenneth M. Coggeshall. 

This is one of the most complete and practical books on electroplating and allied 
processes that has been published as a text for the student or professional plater. 
It is written in simple language and explains aU details of electroplating in a concise 
yet complete manner. It starts at the beginning and gives an elementary outline 
of electricity and chemistry as relates to plating, then considers shop layout and 
equipment and gives all the necessary information to do reliable and profitable electro- 
plating in a modern commercial manner. Full instructions are given for the prepara- 
tion and finishing of the work and formulae and complete directions are included for 
making all kinds of plating solutions, many of these having been trade secrets until 
published in this instruction manual. Anyone interested in practical plating and 
metal finishing will find this book a valuable guide and complete manual of the art. 
Cloth. 142 illustrations. 276 pages. Price $3.00 



FACTORY MANAGEMENT, ETC. 

MODERN MACHINE SHOP CONSTRUCTION, EQUIPMENT AND 
MANAGEMENT. By O. E. Perrigo, M.E. 

The only work published that describes the modern machine shop or manufacturing 
plant from the time the grass is growing on the site intended for it until the finished 
product is shipped. By a careful study of its thirty-six chapters the practical man 
may economically build, efficiently equip, and successfully manage the modern machine 
shop or manufacturing establishment. Just the book needed by those contemplating 
the erection of modern shop buildings, the rebuilding and reorganization of old ones, 
or the introduction of modern shop methods, time and cost systems. It is a book 
written and illustrated by a practical shop man for practical shop men who are too 
busy to read theories and want facts. It is the most complete all-around book of its 
kind ever published. It is a practical book for practical men, from the apprentice in 
the shop to the president in the office. It minutely describes and illustrates the most 
simple and yet the most efficient time and cost system yet devised. 384 pages. 219 
illustrations. Price . $5.00 



FUEL 

COMBUSTION OF COAL AND THE PREVENTION OF SMOKE. By Wm. 

M. Barr. 

This book has been prepared with special reference to the generation of heat by the 
combustion of the common fuels found in the United States, and deals particularly 
with the conditions necessary to the economic and smokeless combustion of bituminous 
coals in Stationary and Locomotive Steam Boilers. 

The presentation of this important subject is systematic and progressive. The ar- 
rangement of the book is in a series of practical questions to which are appended 
accurate answers, which describe in language, free from technicalities, the several 
processes involved in the furnace combustion of American fuels; it clearly states the 
essential requisites for perfect combustion, and points out the best methods for furnace 
construction for obtaining the greatest quantity of heat from any given quality of 
coal. 5th Edition. Nearly 350 pages, fully illustrated. Price. . . . $1.50 



19 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



GAS AND OIL ENGINES 

THE GASOLINE ENGINE ON THE FARM: ITS OPERATION, REPAIR 
AND USES. By Xeno W. Putnam. 

This is a practical treatise on the Gasoline and Kerosene Engine intended for the man 
who wants to know just how to manage his engine and how to apply it to all kinds of 
farm work to the best advantage. 

This book abounds with hints and helps for the farm and suggestions for the home 
and housewife. There is so much of value in this book that it is impossible to ade- 
quately describe it in such small space. Suffice to say that it is the kind of a book 
every farmer will appreciate and every farm home ought to have. Includes selecting 
the most suitable engine for farm work, its most convenient and efficient installation, 
with chapters on troubles, their remedies, and how to avoid them. The care and 
management of the farm tractor in plowing, harrowing, harvesting and road grading 
are fully covered ; also plain directions are given for handling the tractor on the road. 
Special attention is given to relieving farm life of its drudgery by applying power to 
the disagreeable small tasks which must otherwise be done by hand. Many home- 
made contrivances for cutting wood, supplying kitchen, garden, and barn with water, 
loading, hauling and unloading hay, delivering grain to the bins or the feed trough 
are included; also full directions for making the engine milk the cows, churn, wash, 
sweep the house and clean the windows, etc. Very fully illustrated with drawings of 
working parts and cuts showing Stationary. Portable and Tractor Engines doing all 
kinds of farm work. All money-making farms utilize power. Learn how to utilize 
power by reading the pages of this book. It is an aid to the result getter, invaluable 
to the up-to-date farmer, student, blacksmith, implement dealer and, in fact, all who 
can apply practical knowledge of stationary gasoline engines or gas tractors to advan- 
tage. 530 pages. Nearly 180 engravings. Price $3.00 

GASOLINE ENGINES: THEIR OPERATION, USE AND CARE. By A. Hyatt 

Verrill. 

The simplest, latest and most comprehensive popular work published on Gasoline 
Engines, describing what the Gasoline Engine is; its construction and operation; how 
to install it; how to select it; how to use it and how to remedy troubles encountered. 
Intended for Owners, Operators and Users of Gasoline Motors of all kinds. This 
work fully describes and illustrates the various types of Gasoline Engines used in' 
Motor Boats, Motor Vehicles and Stationary Work. The parts, accessories and 
appliances are described, with chapters on ignition, fuel, lubrication, operation and 
engine troubles. Special attention is given to the care, operation and repair of motors, 
with useful hints and suggestions on emergency repairs and makeshifts. A complete 
glossary of technical terms and an alphabetically arranged table of troubles and their 
symptoms form most valuable and unique features of this manual. Nearly every 
illustration in the book is original, having been made by the author. Every page is 
full of interest and value. A book which you cannot afford to be without. 275 pages. 
152 specially made engravings. Price $2.00 

GAS, GASOLINE, AND OIL ENGINES. By Gardner D. Hiscox. 

Just issued, 23d revised and enlarged edition. Every user of a gas engine needs this 
book. Simple, instructive, and right up-to-date. The only complete work on the 
subject. Tells all about the running and management of gas, gasoline and oil engines, 
as designed and manufactured in the United States. Explosive motors for stationary 
marine and vehicle power are fully treated, together with illustrations of their parts 
and tabulated sizes, also their care and running are included. Electric ignition by 
induction coil and jump spark are fully explained and illustrated, including valuable 
information on the testing for economy and power and the erection of power plants. 
The rules and regulations of the Board of Fire Underwriters in regard to the installation 
and management of gasoline motors are given in full, suggesting the safe installation 
of explosive motor power. A list of United States Patents issued on gas, gasoline, and 
oil engines and their adjuncts from 1875 to date is included. 640 pages. 435 engrav- 
ings. Folding plates. Price $3.00 

20 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



GAS ENGINES ANIT PRODUCER-GAS PLANTS. By R. E. Mathot, M.E. 

This is a practical treatise, setting forth the principles of gas engine and producer 
design, the selection and installation of an engine, conditions of perfect operation, 
producer-gas engines and their possibilities ; the care of gas engines and producer-gas 
plants, with a chapter on volatile hydrocarbon and oil engines. A practical guide for 
the gas engine designer, user and engineer in the construction, selection, purchase, in- 
stallation, operation and maintenance of gas engines. Every part of the gas engine is de- 
scribed in detail, tersely, clearly and with a thorough understanding of the requirements of 
the mechanic. Recognizing the need of a volume that would assist the gas engine 
user in understanding the motor upon which he depends for power, the author has 
discussed the subject without the help of any mathematics. Helpful suggestions as to 
the purchase of an engine, its installation, care and operation, form a most valuable 
feature of the book. 6x9 inches. Cloth. 314 pages. 152 illustrations. Price. . $3.00 

GAS ENGINE CONSTRUCTION, OR HOW TO BUILD A HALF-HORSE- 
POWER GAS ENGINE. By Parsell and Weed. 

A practical treatise of 300 pages describing the theory and principles of the action of 
Gas Engines of various types and the design and construction of a half-horse-power 
Gas Engine, with illustrations of the work in actual progress, together with the dimen- 
sioned working drawings, giving clearly the sizes of the various details ; for the student, 
the scientific investigator, and the amateur mechanic. This book treats of the subject 
more from the standpoint of practice than that of theory. The principles of operation 
of Gas Engines are clearly and simply described, and then the actual construction of a 
half -horse-power engine is taken up, step by step, showing in detail the making of the 
Gas Engine. 3d Edition. 300 pages. Price $3.00 

HOW TO RUN AND INSTALL GASOLINE ENGINES. By C. Von Culin. 
Revised and enlarged edition just issued. The object of this little book is to furnish 
a pocket instructor for the beginner, the busy man who uses an engine for pleasure or 
profit, but who does not have the time or inclination for a technical book, but simply 
to thoroughly understand how to properly operate, install and care for his own engine. 
The index refers to each trouble, remedy, and subject alphabetically. Being a quick 
reference to find the cause, remedy and prevention for troubles, and to become an 
expert with his own engine. Pocket size. Paper binding. Price , , 25 cents 

GEARING AND CAMS 



BEVEL GEAR TABLES. By D. Ag. Engstrom. 

A book that will at once commend itself to mechanics and draftsmen. Does away 
with all the trigonometry and fancy figuring on bevel gears, and makes it easy for any- 
one to lay them out or make them just right. There are 36 full-page tables that 
show every necessary dimension for all sizes or combinations you're apt to need. No 
puzzling, figuring or guessing. Gives placing distance, all the angles (including 
cutting angles), and the correct cutter to use. A copy of this prepares you for any- 
thing in the bevel-gear line. 3d Edition. 66 pages $1.50 

CHANGE GEAR DEVICES. By Oscar E. Perrigo. 

A practical book for every designer, draftsman, and mechanic interested in the inven- 
tion and development of the devices for feed changes on the different machines requir- 
ing such mechanism. All the necessary information on this subject is taken up, 
analyzed, classified, sifted, and concentrated for the use of busy men who have not the 
time to go through the masses of irrelevant matter with which such a subject is usu- 
ally encumbered and select such information as will be useful to them. 
It shows just what has been done, how it has been done, when it was done, and who 
did it. It saves time in hunting up patent records and re-inventing old ideas. 3rd 
Edition. » 101 pages $1.50 

DRAFTING OF CAMS. By Louis Rouillion. 

The laying out of cams is a serious problem unless you know how to go at it right. 
This puts you on the right road for practically any kind of cam you are likely to run 
up against. 3d Edition 35 centi 

21 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



HYDRAULICS 

HYDRAULIC ENGINEERING. By Gardner D. Hiscox. 

A treatise on the properties, power, and resources of water for all purposes. Including 
the measurement of streams, the flow of water in pipes or conduits; the horse-power 
of falling water, turbine and impact water-wheels, wave motors, centrifugal, recipro- 
cating and air-lift pumps. With 300 figures and diagrams and 36 practical tables. 
All who are interested in water-works development will find this book a useful one, 
because it is an entirely practical treatise upon a subject of present importance, and 
cannot fail in having a far-reaching influence, and for this reason should have a place 
in the working library of every engineer. Among the subjects treated are: Historical 
Hydraulics, Properties of Water, Measurement of the Flow of Streams; Flow- 
ing Water Suface Orifices and Nozzles ; Flow of Water in Pipes ; Siphons of Various 
Kinds; Dams and Great Storage Reservoirs; City and Town Water Supply; Wells 
and Their Reinforcement; Air Lift Methods of Raising Water; Artesian Wells, 
Irrigation of Arid Districts; Water Power; Water- Wheels ; Pumps and Pumping 
Machinery; Reciprocating Pumps; Hydraulic Power Transmission; Hydraulic 
Mining; Canals; Dredges; Conduits and Pipe Lines; Marine Hydraulics; Tidal and 
Sea Wave Power, etc. 320 pages. Price $4.50 



ICE AND REFRIGERATION 



POCKETBOOK OF REFRIGERATION AND ICE MAKING. By A. J. 

Wallis-Taylor. 

This is one of the latest and most comprehensive reference books published on the 
subject of refrigeration and cola storage. It explains the properties and refrigerating 
effect of the different fluids in use, the management of refrigerating machinery and the 
construction and insulation of cold rooms with their required pipe surface for different 
degrees of cold ; freezing mixtures and non-freezing brines, temperatures of cold rooms 
for all kinds of provisions, cold storage charges for all classes of goods, ice making 
and storage of ice, data and memoranda for constant reference by refrigerating engineers, 
with nearly one hundred tables containing valuable references to every fact and con- 
dition required in the installment and operation of a refrigerating plant. New 
edition just published. Price $2.00 



INVENTIONS— PATENTS 

INVENTORS* MANUAL, HOW TO MAKE A PATENT PAY. 

This is a book designed as a guide to inventors in perfecting their inventions, taking 
out their patents and disposing of them. It is not in any sense a Patent Solicitor's 
Circular nor a Patent Broker's Advertisement. No advertisements of any description 
appear in the work. It is a book containing a quarter of a century's experience of a 
successful inventor, together with notes based upon the experience of many other 
inventors. 

Among the subjects treated in this work are: How to Invent. How to Secure a 
Good Patent. Value of Good Invention. How to Exhibit an Invention. How to 
Interest Capital. How to Estimate the Value of a Patent. Value of Design Patents. 
Value of Foreign Patents. Value of Small Inventions. Advice on Selling Patents. 
Advice on the Formation of Stock Companies. Advice on the Formation of Limited 
Liability Companies. Advice on Disposing of Old Patents. Advice as to Patent 
Attorneys. Advice as to Selling Agents. Forms of Assignments. License and Con- 
tracts. State Laws Concerning Patent Rights. 1900 Census of the United States by 
Counts of Over 10,000 Population. Naw revised and enlarged edition. 144 pages. 
Illustrated. Price. , . , $1.50 

22 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



KNOTS 

KNOTS, SPLICES AND ROPE WORK. By A. Hyatt Verrill. 

This is a practical book giving complete and simple directions for making all the most 
useful and ornamental knots in common use, with chapters on Splicing, Pointing, 
Seizing, Serving, etc. This book is fully illustrated with one hundred and fifty 
original engravings, which show how each knot, tie or splice is formed, and its appear- 
ance when finished. The book will be found of the greatest value to Campers, Yachts- 
men, Travelers, Boy Scouts, in fact, to anyone having occasion to use or handle rope 
or knots for any purpose. The book is thoroughly reliable and practical, and is not 
only a guide, but a teacher. It is the standard work on the subject. Among the 
contents are: 1. Cordage, Kinds of Rope. Construction of Rope, Parts of Rope 
Cable and Bolt Rope. Strength of Rope, Weight of Rope. 2. Simple Knots anu 
Bends. Terms Used in Handling Rope. Seizing Rope. 3. Ties and Hitches. 4. 
Noose, Loops and Mooring Knots. 5. Shortenings, Grommets and Salvages. 6. 
Lashings, Seizings and Splices. 7. Fancy Knots and Rope Work. 104 pages. 154 
original engravings. Price $1.00 

LATHE WORK 

LATHE DESIGN, CONSTRUCTION, AND OPERATION, WITH PRACTICAL 
EXAMPLES OF LATHE WORK. By Oscar E. Perrigo. 
A new revised edition, and the only complete American work on the subject, written 
by a man who knows not only how work ought to be done, but who also knows how 
to do it, and how to convey this knowledge to others. It is strictly up-to-date in its 
descriptions and illustrations. Lathe history and the relations of the lathe to manu- 
facturing are given; also a description of the various devices for feeds and thread 
cutting mechanisms from early efforts in this direction to the present time. Lathe 
design is thoroughly discussed, including back gearing, driving cones, thread-cutting 
gears, and ah the essential elements of the modern lathe. The classification of lathes 
is taken up, giving the essential differences of the several types of lathes including, 
as is usually understood, engine lathes, bench lathes, speed lathes, forge lathes, gap 
lathes, pulley lathes, forming lathes, multiple-spindle lathes, rapid-reduction lathes, 
precision lathes, turret lathes, special lathes, electrically-driven lathes, etc. In addi- 
tion to the complete exposition on construction and design, much practical matter on 
lathe installation, care and operation has been incorporated in the enlarged 1915 edi- 
tion. All kinds of lathe attachments for drilling, milling, etc., are described and 
complete instructions are given to enable the novice machinist to grasp the art of lathe 
operation as well as the principles involved in design. A number of difficult machining 
operations are described at length and illustrated. The new edition has nearly 500 
pages and 350 illustrations. Price $3.00 

LATHE WORK FOR BEGINNERS. By Raymond Francis Yates. 

A simple, straightforward text-book for those desiring to learn the operation of a 
wood-turning or metal-turning lathe. The first chapter tells how to choose a lathe 
and all of the standard types on the market are described. Simple and more advanced 
lathe work is thoroughly covered and the operation of all lathe attachments such as 
millers, grinders, polishers, etc., is described. The treatment starts from the very 
bottom and leads the reader through to a point where he will be able to handle the 
larger commercial machines with very little instruction. The last chapter of the 
book is devoted to things to make on the lathe and includes a model rapid-fire naval 
gun. This is the only book published in this country that treats lathe work from 
the standpoint of the amateur mechanic. 162 illustrations. About 250 pages, 12mo. 
Price $2.00 

TURNING AND BORING TAPERS. By Fred H. Colvin. 

There are two ways to turn tapers; the right way and one other. This treatise has 
to do with the right way; it tells you how to start the work properly, how to set the 
lathe, what tools to use and how to use them, and forty and one other little things 
that you should know. FiftJ? edition. Price , . . 35 cents 

23 



CATALOGUE OF G OOD, PRACTIC AL BOOKS 
LIQUID AIR 

LIQUID AIR AND THE LIQUEFACTION OF GASES. By T. O'Conor Sloane. 
This book gives the history of the theory, discovery, and manufacture of Liquid Air, 
and contains an illustrated description of all the experiments that have excited the 
wonder of audiences all over the country. It shows how liquid air, like water, is 
carried hundreds of miles and is handled in open buckets. It tells what may be ex- 
pected from it in the near future. 

A book that renders simple one of the most perplexing chemical problems of the 
century. Startling developments illustrated by actual experiments. 
It is not only a work of scientific interest and authority, but is intended for the general 
reader, being written in a popular style — easily understood by everyone. Third 
edition. Revised and Enlarged. 394 pages. New Edition. Price . . . $3.00 

LOCOMOTIVE ENGINEERING 



AIR-BRAKE CATECHISM. By Robert H. Blackall. 

This book is a standard text-book. It covers the Westinghouse Air-Brake Equipment, 
including the No. 5 and the No. 6 E. T. Locomotive Brake Equipment; the K (Quick 
Service) Triple Valve for Freight Service; and the Cross-Compound Pump. The 
operation of all parts of the apparatus is explained in detail, and a practical way of 
finding their peculiarities and defects, with a proper remedy, is given. It contains 
2,000 questions with their answers, which will enable any railroad man to pass any 
examination on the subject of Air Brakes. Endorsed and used by air-brake instruc- 
tors and examiners on nearly every railroad in the United States. 28th Edition. 411 
pages, fully illustrated with colored plates and diagrams. Price $2.50 

COMBUSTION OF COAL AND THE PREVENTION OF SMOKE. By Wm. 
M. Barr. 

This book has been prepared with special reference to the generation of heat by tho 
combustion of the common fuels found in the United States and deals particularly 
with the conditions necessary to the economic and smokeless combustion of bituminous 
coal in Stationary and Locomotive Steam Boilers. 

Presentation of this important subject is systematic and progressive. The ar- 
ransement of the book is in a series of practical questions to which are appended 
accurate answers, which describe in language free from technicalities the several 
processes involved in the furnace combustion of American fuels; it clearly states the 
essential requisites for perfect combustion, and points out the best methods of furnace 
construction for obtaining the greatest quantity of heat from any given quality of 
coal. Nearly 350 pages, fully illustrated. Price $1.50 

DIARY OF A ROUND-HOUSE FOREMAN. By T. S. Reilly. 

This is the greatest book of railroad experiences ever published. Containing a fund of 
information and suggestions along the line of handling men, organizing, etc., that one 
cannot afford to miss. 158 pages. Price $1.50 

LINK MOTIONS, VALVES AND VALVE SETTING. By Fred H. Colvin, 
Associate Editor of American Machinist. 
A handy book for the engineer or machinist that clears up the mysteries of valve 
setting. Shows the different valve gears in use, how they work, and why. Piston 
and slide valves of different types are illustrated and explained. A book that every 
railroad man in the motive power department ought to have. Contains chapters on 
Locomotive Link Motion, Valve Movements, Setting Slide Valves, Analysis by 
Diagrams, Modern Practice, Slip of Block, Slice Valves, Piston Valves, Setting Piston 
Valves, Joy-Allen Valve Gear, Walschaert Valve Gear, Gooch Valve Gear, Alfree- 
Hubbell Valve Gear, etc., etc. 3rd Edition, 101 *>ages. Fully illustrated. Price 

75 cents 

24 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

LOCOMOTIVE BOILER CONSTRUCTION. By Frank A. Kleineans. 

The construction of boilers in general is treated, and, following this, the locomotive 
boiler is taken up in the order in which its various parts go through the shop. She org 
all types of boilers used: gives details of construction; practical facts, such as life of 
riveting, punches and dies; work done per day, allowance for bending and flanging 
sheets, and other data. Including the recent Locomotive Boiler Inspection Laws 
and Examination Quastions with their answers for Government Inspectors. Contains 
chapters on Laying Out Work; Flanging and Forging; Punching; Shearing; Plate 
Planing; General Tables; Finishing Parts; Bending; Machinery Parts; Riveting; 
Boiler Details; Smoke Box Details; Assembling and Calking; Boiler Shop 
Machinery, etc., etc. 

There isn't a man who has anything to do with boiler work, either new or repair work, 
who doesn't need this book. The manufacturer, superintendent, foreman, and boiler 
worker — all need it. No matter what the type of boiler, you'll find a mint of informa- 
tion that you wouldn't be without. 451 pages, 334 illustrations, five large folding 
plates. Price $3.50 

LOCOMOTIVE BREAKDOWNS AND THEIR REMEDIES. By Geo. L. 
Fowler. Revised 'by Wm. W. Wood, Air-Brake Instructor. Just issued. 
Revised pocket edition. 

It is out of the question to try and tell you about every subject that is covered in this 
pocket edition of Locomotive Breakdowns. Just imagine all the common troubles 
that an engineer may expect to happen some time, and then add all of the unexpected 
ones, troubles that could occur, but that you have never thought about, and you will 
find that they are all treated with the very best methods of repair Walschaert 
Locomotive Valve Gear Troubles, Electric Headlight Troubles, as well as Questions 
and Answers on the Air Brake are all included. 293 pages. 8th Revised Edition. 
Fully illustrated $1.50 

PRACTICAL INSTRUCTOR AND REFERENCE BOOK FOR LOCOMOTIVE 
FIREMEN AND ENGINEERS. By Chas. F. Lockhart. 

An entirely new book on the Locomotive. It appeals to every railroad man, as it 
tells him how things are done and the right way to do them. Written by a man who 
has had years of practical experience in locomotive shops and on the road firing and 
running. The information given in this book cannot be found in any other similar 
treatise. Eight hundred and fifty-one questions with their answers are included, 
which will prove specially helpful to those preparing for examination. Practical 
information on: The Construction and Operation of Locomotives; Breakdowns and 
their Remedies; Air Brakes and Valve Gears. Rules and Signals are handled in a 
thorough manner. As a book of reference it cannot be excelled. The book is divided 
into six parts, as follows: 1. The Fireman's Duties. 2. General Description of the 
Locomotive. 3. Breakdowns and their Remedies. 4. Air Brakes. 5. Extracts 
from Standard Rules. 6. Questions for Examination. The 851 questions have been 
carefully selected and arranged. These cover the examinations required by the 
different railroads. 368 pages. 88 illustrations. Price $2.50 

PREVENTION OF RAILROAD ACCIDENTS, OR SAFETY IN RAILROADING. 

By George Bradshaw. 

This book is a heart-to-heart talk with Railroad Employees, dealing with facts, not 
theories, and showing the men in the ranks, from every-day experience, how accidents 
occur and how they may be avoided. The book is illustrated with seventy original 
photographs and drawings showing the safe and unsafe methods of work. No vision- 
ary schemes, no ideal pictures. Just plain facts and Practical Suggestions are given. 
Every railroad employee who reads the book is a better and safer man to have in 
railroad service. It gives just the information which will be the means of preventing 
many injuries and deaths. All railroad employees should procure a copy; read it, 
and do your part in preventing accidents. 1G9 pages. Pocket size. Fully illustrated. 
Price 50 cents 

2S 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

TRAIN RULE EXAMINATIONS MADE EASY. By G. E. Collingwood. 

This is the only practical work on train rules in print. Every detail is covered, and 
puzzling points are explained in simple, comprehensive language, making it a practical 
treatise for the Train Dispatcher, Engineman, Trainman, and all others who have to 
do with the movements of trains. Contains complete and reliable information of the 
Standard Code of Train Rules for single track. Shows Signals in Colors, as used on 
the different roads. Explains fully the practical application of train orders, giving a 
clear and definite understanding of all orders which may be used. The meaning and 
necessity for certain rules are explained in such a manner that the student may know 
beyond a doubt the rights conferred under any orders he may receive or the action 
required by certain rules. As nearly all roads require trainmen to pass regular exami- 
nations, a complete set of examination questions, with their answers, are included. 
These will enable the student to pass the required examinations with credit to himself 
and the road for which he works. Second Edition revised. 234 pages. Fully illus- 
trated with Train Signals in Colors. Price $1.50 

THE WALSCHAERT AND OTHER MODERN RADIAL VALVE GEARS FOR 
LOCOMOTIVES. By Wm. W. Wood. 

If you would thoroughly understand the Walschaert Valve, Gear you should possess a 
copy of this book, as the author takes the plainest form of a steam engine — a stationary 
engine in the rough, that will only turn its crank in one direction — and from it builds 
up — with the reader's help — a modern locomotive equipped with the Walschaert 
Valve Gear, complete. The points discussed are clearly illustrated ; two large folding 
plates that show the positions of the valves of both inside or outside admission type, as 
well as the finks and other parts of the gear when the crank is at nine different points 
in its revolution, are especially valuable in making the movement clear. These employ 
sliding cardboard models which are contained in a pocket in the cover. 
The book is divided into five general divisions, as follows: 1. Analysis of the gear. 
2. Designing and erecting the gear. 3. Advantages of the gear. 4. Questions and 
answers relating to the Walschaert Valve Gear. 5. Setting valves with the Wal- 
schaert Valve Gear; the three primary, types of locomotive valve motion; modern 
radial valve gears other than the Walschaert; the Hobart All-free Valve and Valve 
Gear, with questions and answers on breakdowns; the Baker-Pilliod Valve Gear; the 
Improved Baker-Pilliod Valve Gear, with questions and answers on breakdowns. 
The questions with full answers given will be especially valuable to firemen and engi- 
neers in preparing for an examination for promotion. 245 pages. Fully illustrated. 
Third Revised New Edition. Price $2.50 

WESTINGHOUSE E-T AIR-BRAKE INSTRUCTION POCKET BOOK. By 

Wm. W. Wood, Air-Brake Instructor. 

Here is a book for the railroad man, and the man who aims to be one. It is without 
doubt the only complete work published on the Westinghouse E-T Locomotive Brake 
Equipment. Written by an Air-Brake Instructor who knows just what is needed. It 
covers the subject thoroughly. Everything about the New Westinghouse Engine and 
Tender Brake Equipment, including the standard No. 5 and the Perfected No. 6 
style of brake, is treated in detail. Written in plain English and profusely illustrated 
with Colored Plates, which enable one to trace the flow of pressures throughout the 
entire equipment. The best book ever published on the Air Brake. Equally good for 
the beginner and the advanced engineer. Will pass anyone through any examination. 
It informs and enlightens you on every point. Indispensable to every engineman and 
trainman. 

Contains examination questions and answers on the E-T equipment. Covering what 
the E-T Brake is. How it should be operated. What to do when defective. Not a 
question can be asked of the engineman up for promotion, on either the No. 5 or the 
No. 6 E-T equipment, that is not asked and answered in the book. If you want to 
thoroughly understand the E-T equipment get a copy of this book. It covers every 
detail. Makes Air-Brake troubles and examinations easy. Second Revised and 
Enlarged Edition. Price _ $2.50 



26 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



MACHINE-SHOP PRACTICE 

AMERICAN TOOL MAKING AND INTERCHANGEABLE MANUFACTUR- 
ING. By J. V. Woodworth. 

A "shoppy" book, containing no theorizing, no problematical or experimental devices, 
there are no badly proportioned and impossible diagrams, no catalogue cuts, but a 
valuable collection of drawings and descriptions of devices, the rich fruits of the author's 
own experience. In its 500-odd pages the one subject only, Tool Making, and what- 
ever relates thereto, is dealt with. The work stands without a rival. It is a complete 
practical treatise on the art of American Tool Making and system of interchangeable 
manufacturing as carried on to-day in the United States. In it are described and 
illustrated all of the different types and classes of small tools, fixtures, devices, and 
special appliances which are in general use in all machine-manufacturing and metal- 
working establishments where economy, capacity, and interchangeability in the pro- 
duction of machined metal parts are imperative. The science of jig making is exhaus- 
tively discussed, and particular attention is paid to drill jigs, boring, profiling and milling 
fixtures and other devices in which the parts to be machined are located and fastened 
within the contrivances. All of the tools, fixtures, and devices illustrated and de- 
scribed have been or are used for the actual production of work, such as parts of drill 
presses, lathes, patented machinery, typewriters, electrical apparatus, mechanical ap- 
pliances, brass goods, composition parts, mould products, sheet metal articles, drop- 
forgings, jewelry, watches, medals, coins, etc. 3rd Edition. 531 pages. Price $4.50 

MACHINE-SHOP ARITHMETIC. By Colvin-Cheney., 

This is an arithmetic of the things you have to do with daily. It tells you plainly 
about: how to find areas in figures; how to find surface or volume of balls or spheres; 
handy ways for calculating; about compound gearing; cutting screw threads on any 
lathe; drilling for taps; speeds of drills; taps, emery wheels, grindstones, milling 
cutters, etc. : all about the Metric system with conversion tables ; properties of metals ; 
strength of bolts and nuts ; decimal equivalent of an inch. All sorts of machine-shop 
figuring and 1,001 other things, any one of which ought to be worth more than 
the price of this book to you, and it saves you the trouble of bothering the boss. 7th 
edition. 131 pages. Price 75 cents 

MODERN MACHINE-SHOP CONSTRUCTION, EQUIPMENT AND MAN- 
AGEMENT. By Oscar E. Perrigo. 

The only work published that describes the Modern Shop or Manufacturing Plant 
from the time the grass is growing on the site intended for it until the finished product 
is shipped. Just the book needed by those contemplating the erection of modern shop 
buildings, the rebuilding and reorganization of old ones, or the introduction of Modern 
Shop Methods, time and cost systems. It is a book written and illustrated by a prac- 
tical shop man for practical shop men who are too busy to read theories and want facts. 
It is the most complete all-round book of its kind ever published . . 384 pages. 
219 original and specially-made illustrations. Revised and Enlarged Edition. 
Price $5.00 

«« SHOP KINKS." By Robert Grimshaw. 

A book of 400 pages and 222 illustrations, being entirely different from any other 
book on machine-shop practice. Departing from conventional style, the author 
avoids universal or common shop usage and limits his work to showing special ways 
of doing things better, more cheaply and more rapidly than usual. As a result the 
advanced methods of representative establishments of the world are placed at the 
disposal of the reader. This book shows the proprietor where large savings are possible, 
and how products may be improved. To the employee it holds out suggestions that, 

froperly applied, will hasten his advancement. No shop can afford to be without it. 
t bristles with valuable wrinkles and helpful suggestions. It will benefit all. from 
apprentice to proprietor. 5th edition. Price $3.00 

THREADS AND THREAD-CUTTING. By Colvin and Stabel. 

This clears up many of the mysteries of thread-cutting, such as double and triple 
threads, internal threads, catching threads, use of hobs, etc. Contains a lot of useful 
hints and several tables. 4th edition. Price . _ 35 cents 



27 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



THE WHOLE FIELD OF MECHANICAL MOVEMENTS 
COVERED BY MR. HXSCOX'S TWO BOOKS 



We publish two books by Gardner D. Hiscox that will keep you from "inventing" things 
"hat have been done before, and suggest ways of doing things that you have not thought of 
before. Many a man spends time and money, pondering over some mechanical problem, 
only to learn, after he has solved the problem, that the same thing has been accomplished 
and put in practice by others long before. Time and money spent in an effort to accom- 
plish what has already been accomplished are time and money LOST. The whole field 
of mechanics, every known mechanical movement, and practically every device is covered 
by these two books. If the thing you want has been invented, it is illustrated in them. If 
it hasn't been invented, then you'll find in them the nearest things to what you want, some 
movements or devices that will apply in your case, perhaps; or which will give you a key 
from which to work. No book or set of books ever published is of more real value to the 
Inventor, Draftsman, or practical Mechanic than the two volumes described below. 

MECHANICAL MOVEMENTS, POWERS, AND DEVICES. By Gardner D. 

Hiscox. 

This is a collection of 1,890 engravings of different mechanical motions and appliances, 
accompanied by appropriate text, making it a book of great value to the inventor, 
the draftsman, and to all readers with mechanical tastes. The book is divided into 
eighteen sections or chapters, in which the subject-matter is classified under the follow- 
ing heads: Mechanical Powers; Transmission of Power; Measurement of Power; 
Steam Power; Air Power Appliances; Electric Power and Construction; Navigation 
and Roads; Gearing; Motion and Devices; Controlling Motion; Horological; 
Mining; Mill and Factory Appliances; Construction and Devices; Drafting Devices; 
Miscellaneous Devices, etc. 15th edition enlarged. 400 octavo pages. Price . $4.00 

MECHANICAL APPLIANCES, MECHANICAL MOVEMENTS AND NOVEL- 
TIES OF CONSTRUCTION. By Gardner D. Hiscox. 

This is a supplementary volume to the one upon mechanical movements. Unlike the 
first volume, which is more elementary in character, this volume contains illustrations 
and descriptions of many combinations of motions and of mechanical devices and 
appliances found in different lines of machinery, each device being shown by a line 
drawing with a description showing its working parts and the method of operation. 
From the multitude of devices described and illustrated might be mentioned, in 
passing, such items as conveyors and elevators, Prony brakes, thermometers, various 
types of boilers, solar engines, oil-fuel burners, condensers, evaporators, Corliss and 
other valve gears, governors, gas engines, water motors of various descriptions, air- 
ships, motors and dynamos, automobile and motor bicycles, railway lock signals, 
car couplers, link and gear motions, ball bearings, breech block mechanism for heavy 
guns, and a large accumulation of others of equal importance. 1,000 specially made 
engravings. 396 octavo pages. 4th Edition enlarged. Price $4.00 

SHOP PRACTICE FOR HOME MECHANICS. By Raymond Francis Yates. 

A thoroughly practical and helpful treatment prepared especially for those who have 
had little or no experience in shop work. The introduction is given over to an ele- 
mentary explanation of the fundamentals of mechanical science. This is followed 
by several chapters on the use of small tools and mechanical measuring instruments. 
Elementary and more advanced lathe work is treated in detail and directions given 
for the construction of a number of useful shop appliances. Drilling and reaming, 
heat treatment of tool steel, special lathe operations, pattern making, grinding, and 
grinding operations, home foundry work, etc., make up the rest of the volume. The 
book omits nothing that will be of use to those who use tools or to those who wish 
to learn the use of tools The great number of clear engravings (over 300) add 
tremendously to the text matter and tp the value of the volume as a visual instructor. 
Octavo, 320 pages, 309 engravings. Price , ,*,,,«,»#, $3.00 



28 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



MACHINE-SHOP TOOLS AND SHOP PRACTICE. By W. H. Vandervoort. 

A work of 552 pages and 672 illustrations, describing in every detail the construction, 
operation, and manipulation of both hand and machine tools. Includes chapters 
on filing, fitting, and scraping surfaces; on drills, reamers, taps, and dies; the lathe 
and its tools; planers, shapers, and their tools; milling machines and cutters; gear 
cutters and gear cutting; drilling machines and drill work; grinding machines and 
their work; hardening and tempering; gearing, belting, and transmission machinery; 
useful data and tables. 7th Edition. 552 pages. 672 illustrations. Price $4.50 

COMPLETE PRACTICAL MACHINIST. By Joshua Rose. 

The new, twentieth revised and enlarged edition is now ready. This is one of the 
best-known books on machine-shop work, and written for the practical workman 
in the language of the workshop. It gives full, practical instructions on the use of 
all kinds of metal-working tools, both hand and machine, and tells how the work 
should be properly done. It covers lathe work, vise work, drills and drilling, taps 
and dies, hardening and tempering, the making and use of tools, tool grinding, mark- 
ing out work, machine tools, etc. No machinist's library is complete without this 
TOlume. 20th Edition. 547 pages. 432 illustrations. Price .... $3.00 

HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED 
TRADES. Edited by Joseph G. Horner, A.M.I.Mech.E. 

This book covers the entire practice of Civil and Mechanical Engineering. The 
best known experts in all branches of engineering have contributed to these volumes. 
The Cyclopedia is admirably well adapted ^o the needs of the beginner and the self- 
taught practical man, as well as the mechanical engineer, designer, draftsman, shop 
superintendent, foreman and machinist. 

It is a moderm treatise in five volumes. Handsomely bound in half morocco, each 
volume containing nearly 500 pages, with thousands of illustrations, including dia- 
grammatic and sectional drawings with full explanatory details. Five large volumes. 
Price $30.00 

MODEL MAKING Including Workshop Practice, Design and Construction of 
Models. Edited by Raymond F. Yates. Editor of "Everyday Engineering 
Magazine." 

This book will help you to become a better mechanic. It is full of suggestions for those 
who like to make things, amateur and professional alike. It has been prepared es- 
pecially for men with mechanical hobbies. Some may be engineers, machinists, jew- 
elers, pattern makers, office clerks or bank presidents. Men from various walks of 
life have a peculiar interest in model engineering. Model Making will be a help and 
an inspiration to such men. It tells them "how -to-do" and "how-to-make" things 
in simple, understandable terms. Not only this, it is full of good, clear working 
drawings and photographs of the models and apparatus described. Each model has 
been constructed and actually works if it is made according to directions. 379 pages. 
300 illustrations. Price $3.00 

ABRASIVES AND ABRASIVE WHEELS. By Fred B. Jacobs. 

A new book for everyone interested in abrasives or grinding. A careful reading of 
the book will not only make mechanics better able to use abrasives intelligently, but 
it will also tell the shop superintendent of many short cuts and efficiency-increasing 
kinks. The economic advantages in using large grinding wheels are fully explained, 
together with many other things that will tend to give the superintendent or workman 
a keen insight into abrasive engineering. 340 pages. 174 illustrations. This is an 
indispensable book for every machinist. Price $3.00 

HOME MECHANIC'S WORKSHOP COMPANION. By Andrew Jackson, Jr. 

This treatise includes a compilation of useful suggestions that cannot fail to interest 
the handy man, and while it is not intended for mechanical experts or scientists, it will 
prove to be a veritable store of information for anyone who desires to rig up a small 
shop where odd jobs can be carried on. Price 75 cents 

29 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



MARINE ENGINEERING 

THE NAVAL ARCHITECT'S AND SHIPBUILDER'S POCKETBOOK. Of 

Formulae, Rules, and Tables and Marine Engineer's and Surveyor's Handy 
Book of Reference. By Clement Mackrow and Lloyd Woollard. 

The twelfth revised and enlarged edition of this most comprehensive work has just 
been issued. It is absolutely indispensable to all engaged in the Shipbuilding Industry, 
as it condenses into a compact form all data and formulae] that are ordinarily required. 
The book is completely up to date, including among other subjects a section on 
Aeronautics. 760 pages, limp leather binding. Price $6.00 

MARINE ENGINES AND BOILERS— THEIR DESIGN AND CONSTRUC- 
TION. THE STANDARD BOOK. By Dr. G. Bauer, Leslie S. Robertson 
and S. Bryan Donkin. 

In the words of Dr. Bauer, the present work owes its origin to an oft felt want of a 
condensed treatise embodying the theoretical and practical rules used in designing 
marine engines and boilers. The fact that the original German work was written by 
the chief engineer of the famous Vulcan Works, Stettin, is in itself a guarantee that 
this book is in all respects thoroughly up-to-date, and that it embodies all the in- 
formation which is necessary for the design and construction of the highest types of 
marine engines and boilers. It may be said that the motive power which Dr. Bauer 
has placed in the fast German liners that have been turned out of late years from the 
Stettin Works represent the very best practice in marine engineering of the present 
day. The work is clearly written, thoroughly systematic, theoretically sound; while 
the character of the plans, drawings, tables, and statistics is without reproach. The 
illustrations are careful reproductions from actual working drawings, with some well- 
executed photographic views of completed engines and boilers. Fifth impression. 
,744 pages. 550 illustrations, and numerous tables. Cloth. Price . . . $10.00 

MANUAL TRAINING 

ECONOMICS OF MANUAL TRAINING. By Louis Rotjillion. 

The only book published that gives just the information needed by all interested in 
Manual Training, regarding Buildings, Equipment, and Supplies. Shows exactly 
what is needed for all grades of the work from the Kindergarten to the High and 
Normal School. Gives itemized lists of everything used in Manual Training Work 
and tells just what it ought to cost. Also shows where to buy supplies, etc. Contains 
, 174 pages, and is fully illustrated. 2d edition. Price $2.00 

MOTOR BOATS 

MOTOR BOATS AND BOAT MOTORS. By Victor W. Page and A. 0. Leitch. 
All who are interested in motor boats, either as owners, builders or repairmen, will 
find this latest work a most comprehensive treatise on the design, construction, opera- 
tion and repair of motor boats and their power plants. It is really two complete 
books in one cover as it consists of two parts, each complete in itself. Part One deals 
with The Hull and Its Fittings, Part Two considers The Power Plant and Its 
Auxiliaries. A valuable feature of this book is the complete set of dimensioned 
working drawings detailing the construction of five different types of boats ranging 
from a 16-foot shallow draft, tunnel, stern general utility craft to a 25-foot cabin 
cruiser. These plans are by A. C. Leitch, a practical boat builder and expert naval 
architect, and are complete in every particular. Full instructions are given for the 
selection of a power plant and its installation in the hull. Valuable advice is included 
on boat and engine operation and latest designs of motors are described and illustrated. 
The instructions for overhauling boat and engine are worth many times the small 
cost of the book. It is a comprehensive work of reference for all interested in motor 
boating in any of its phases. Octavo. Cloth. 372 illustrations. 524 pages. 
Price 7 $4.00. 



30 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



MOTORCYCLES 

MOTORCYCLES AND SIDE CARS, THEIR CONSTRUCTION, MANAGE- 
MENT AND REPAIR. By Victor W. Page, M.E. 

The only complete work published for the motorcyclist and repairman. Describes 
fullv all leading types of machines, their design, construction, maintenance, operation 
and" repair. This treatise outlines fully the operation of two- and four-cycle power 
plants and all ignition, carburetion and lubrication ss'stems in detail. Describes all 
representative types of free engine clutches, variable speed gears and power trans*- 
mission systems. Gives complete instructions for operating and repairing all tj-pes. 
Considers fully electric self-starting and lighting systems, all types of spring frames 
and spring forks and shows leading control methods. For those desiring technical 
information a complete series of tables and many formulae to assist in designing are 
included. The work tells how to figure power needed to climb grades, overcome air 
resistance and attain high speeds. It shows how to select gear ratios for various 
weights and powers, how to figure braking efficiency required, gives sizes of belts and 
chains to transmit power safely, and shows how to design sprockets, belt pulleys, etc. 
This work also includes complete formulae for figuring horse-power, shows how dyna- 
mometer tests are made, defines relative efficiency of air- and water-cooled engines, plain 
and anti-friction bearings and many other data of a practical, helpful, engineering 
nature. Remember that you get this information in addition to the practical de- 
scription and instructions which alone are worth several times the price of the book. 
2nd Edition Revised and Enlarged. 693 pages. 371 specially made illustrations. 
Cloth. Price $3.00 

WHAT IS SAID OP THIS BOOK: 

" Here is a book that should be in the cycle repairer's kit." — American Blacksmith. 
" The best way for any rider to thoroughly understand his machine, is to get a copy 
of this book; it is worth many times its price." — Pacific Motorcyclist, 



PATTERN MAKING 



PRACTICAL PATTERN MAKING. By F. W. Barrows. 

This book, now in its second edition, is a comprehensive and entirely practical treatise 
on the subject of pattern making, illustrating pattern work in both wood and metal, 
and with definite instructions on the use of plaster of Paris in the trade. It gives 
specific and detailed descriptions of the materials used by pattern makers and de- 
scribes the tools, both those for the bench and the more interesting machine tools, 
having complete chapters on the Lathe, the Circular Saw, and the Band Saw. It gives 
many examples of pattern work, each one fully illustrated and explained with much 
detail. These examples, in their great variety, offer much that will be found of 
interest to all pattern makers, and especially to the younger ones, who are seeking 
information on the more advanced branches of their trade. 

In this second edition of the work will be found much that is new, even to those who 
have long practiced this exacting trade. In the description of patterns as adapted 
to the Moulding Machine many difficulties which have long prevented the rapid and 
economical production of castings are overcome; and this great, new branch of the 
trade is given much space. Stripping plate and stool plate work and the less expen- 
sive vibrator, or rapping plate work, are all explained in detail. 

Plain, everyday rules for lessening the cost of patterns, with a complete system of 
cost keeping, a detailed method of marking, applicable to all branches of the trade, 
with complete information showing what the pattern is, its specific title, its cost, 
date of production, material of which it is made, the number of pieces and core- 
boxes, and its location in the pattern safe, all condensed into a most complete card 
record, with cross index. 

The book closes with an original and practical method for the inventory and valua- 
tion of patterns. 2nd Edition. Containing nearly 350 pages and 170 illustra- 
tions. Price $2.50 



3» 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



PERFUMERY 

PERFUMES AND COSMETICS, THEIR PREPARATION AND MANUFAC- 
TURE. By G. W. Askinson, Perfumer. 

A comprehensive treatise, in which there has been nothing omitted that could be of 
value to the perfumer or manufacturer of toilet preparations. Complete directions 
for making handkerchief perfumes, smelling-salts, sachets, fumigating pastilles; 
preparations for the care of the skin, the mouth, the hair, cosmetics, hair dyes and 
other toilet articles are given, also a detailed description of aromatic substances ; their 
nature, tests of purity, and wholesale manufacture, including a chapter on synthetic 
products, with formulas for their use. A book of general, as well as professional in- 
terest, meeting the wants not only of the druggist and perfume manufacturer, but 
also of the general public. Fourth Edition much enlarged and brought up-to-date. 
Nearly 400 pages, illustrated. Price $5.00 

WHAT IS SAID OF THIS BOOK: 
•' The most satisfactory work on the subject of Perfumery that we have ever seen. 
*' We feel safe in saying that here is a book on Perfumery that will not disappoint you, 
for it has practical and excellent formulae that are within youTj ability to prepare 
readily. 

•* We recommend the volume as worthy of confidence, and say that no purchaser will be 
disappointed in securing from its pages good value for its cost, and a large dividend 
on the same, even if he should use but one per cent of its working formulae. There 
is money in it for every user of its information." — Pharmaceutical Record. 



PLUMBING 

MECHANICAL DRAWING FOR PLUMBERS. By R. M. Starbuck. 

A concise, comprehensive and practical treatise on the subject of mechanical drawing 
in its various modern applications to the work of all who are in any way connected 
with the plumbing trade. Nothing will so help the plumber in estimating and in 
explaining work to customers and workmen as a knowledge of drawing, and to the 
workman it is of inestimable value if he is to rise above his position to positions of 
greater responsibility. Among the chapters contained are: 1. Value to plumber of 
knowledge of drawing; tools required and their use; common views needed in mechan- 
ical drawing. 2. Perspective versus mechanical drawing in showing plumbing con- 
struction. 3. Correct and incorrect methods in plumbing drawing ; plan and elevation 
explained. 4. Floor and cellar plans and elevation; scale drawings; use of triangles. 
5. Use of triangles; drawing of fittings, traps, etc. 6. Drawing plumbing elevations 
and fittings. 7. Instructions in drawing plumbing elevations. 8. The drawing of 
plumbing fixtures ; scale drawings. 9. Drawings of fixtures and fittings. 10. Inking 
of drawings. 11. Shading of drawings. 12. Shading of drawings. 13. Sectional 
drawings; drawing of threads. 14. Plumbing elevations from architect's plan. 15. Ele- 
vations of separate parts of the plumbing system. 16. Elevations from the architect's 
plans. 17. Drawings of detail plumbing connections. 18. Architect's plans and plumb- 
ing elevations of residence. 19. Plumbing elevations of residence (continued) ; plumb- 
ing plans for cottage. 20. Plumbing elevations; roof connections. 21. Plans and 
plumbing elevations for six-flat building. 22. Drawing of various parts of the plumb- 
ing system; use of scales. 23. Use of architect's scales. 24. Special features in the 
illustrations of country plumbing. 25. Drawing of wrought-iron piping, valves, radia- 
tors, coils, etc. 26. Drawing of piping to illustrate heating systems. 150 illustrations. 
Price r • $2.00 



32 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

r 

MODERN PLUMBING ILLUSTRATED. By R. M. StarbucK. 

This book represents the highest standard of plumbing work. It has been adopted 
and used as a reference book by the United States Government, in its sanitary work in 
Cuba, Porto Rico, and the Philippines, and by the principal Boards of Health of the 
United States and Canada. 

It gives connections, sizes and working data for all fixtures and groups of fixtures. It 
is helpful to the master plumber in demonstrating to his customers and in figuring 
work. It gives the mechanic and student quick and easy access to the best modern 
plumbing practice. Suggestions for estimating plumbing construction are contained 
in its pages. This book represents, in a word, the latest and best up-to-date practice 
and should be in the hands of every architect, sanitary engineer and plumber who 
wishes to keep himself up to the minute on this important feature of construction. 
Contains following chapters, each illustrated with a full-page plate: Kitchen sink, 
laundry tubs, vegetable wash sink; lavatories, pantry sinks, contents of marble slabs; 
bath tub, foot and sitz bath, shower bath; water closets, venting of water closets; low- 
down water closets, water closets operated by flush valves, water closet range ; slop sink, 
urinals, the bidet; hotel and restaurant sink, grease trap ; refrigerators, safe wastes, laun- 
dry waste, lines of refrigerators, bar sinks, soda fountain sinks; horse stall, frost-proof 
water closets; connections for S traps, venting; connections for drum traps; soil pipe 
connections; supporting of soil pipe; main trap and fresh air inlet; floor drains and 
cellar drains, subsoil drainage; water closets and floor connections; local venting; 
connections for bath rooms; connections for bath rooms, continued; connections for 
bath rooms, continued; connections for bath rooms, continued; examples of poor 
practice; roughing work ready for test; testing of plumbing system; method of con- 
tinuous venting; continuous venting for two-floor work; continuous venting for two 
lines of fixtures on three or more floors; continuous venting of water closets; plumb- 
ing for cottage house; construction for cellar piping; plumbing for residence, use of 
Bpecial fittings; plumbing for two-fiat house; plumbing for apartment building, plumb- 
ing for double apartment building; plumbing for office building; plumbing for public 
toilet rooms; plumbing for public toilet rooms, continued; plumbing for bath estab- 
lishment; plumbing for engine house, factory plumbing; automatic flushing for 
schools, factories, etc.; use of flushing valves; urinals for public toilet rooms; the 
Durham system, the destruction of pipes by electrolysis; construction of work without 
use of lead; automatic sewage lift; automatic sump tank; country plumbing; construc- 
tion of cesspools ; septic tank and automatic sewage siphon ; country plumbing ; water 
supply for country house; thawing of water mains and service by electricity; double 
boilers; hot water supply of large buildings; automatic control of hot water tank; sug- 
gestion for estimating plumbing construction. 407 octavo pages, fully illustrated by 58 
full-page engravings. Third, revised and enlarged edition just issued. Price . $5.00 

STANDARD PRACTICAL PLUMBING. By R. M. Starbuck. 

A complete practical treatise of 450 pages covering the subject of Modern Plumbing 
in all its branches, a large amount of space being devoted to a very complete and 
practical treatment of the subject of Hot Water Supply and Circulation and Range 
Boiler Work. Its thirty chapters include about every phase of the subject one can 
think of, making it an indispensable work to the master plumber, the journeyman 
plumber, and the apprentice plumber, containing chapters on: the plumber's tools; 
wiping solder; composition and use; joint wiping; lead work; traps; siphonage of 
traps; venting; continuous venting; house sewer and sewer connections; house drain; 
soil piping, roughing; main trap and fresh air inlet; floor, yard, cellar drains, rain 
leaders, etc.; fixture wastes; water closets; ventilation; improved plumbing connec- 
tions; residence plumbing; plumbing for hotels, schools, factories, stables, etc.; 
modern country plumbing; filtration of sewage and water supply; hot and cold 
supply; range boilers; circulation; circulating pipes; range boiler problems; hot 
water for large buildings; water lift and its use; multiple connections for hot water 
boilers; heating of radiation by supply system; theory for the plumber; drawing for 
the plumber. Fully illustrated by 347 engravings. Price $3.50 



33 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



RECIPE BOOK 

HENLEY'S TWENTIETH CENTURY BOOK OF RECIPES, FORMULAS AND 
PROCESSES. Edited by Gardner D. Hiscox. 

The most valuable Techno-chemical FormvuVBook published, including over 10,000 
selected scientific, chemical, technological, and practical recipes and processes. 
This is the most complete Book of Formulas ever published, giving thousands of 
recipes for the manufacture of valuable articles for everyday use. Hints, Helps, 
Practical Ideas, and Secret Processes are revealed within its pages. It covers every 
branch of the useful arts and tells thousands of ways of making money, and is just the 
book everyone should have at his command. 

Modern in its treatment of every subject that properly falls within its scope, the book 
may truthfully be said to present the very latest formulas to be found in the arts and 
industries, and to retain those processes which long experience has proven worthy of a 
permanent record. To present here even a limited number of the subjects which find 
a place in this valuable work would be difficult. Suffice to say that in its pages will 
be found matter of intense interest and immeasurably practical value to the scientific 
amateur and to him who wishes to obtain a knowledge of the many processes used in 
the arts, trades and manufacture, a knowledge which will render his pursuits more 
instructive and remunerative. Serving as a reference book to the small and large 
manufacturer and supplying intelligent seekers with the information necessary to 
conduct a process, the work will be found of inestimable worth to the Metallurgist, the 
Photographer, the Perfumer, the Painter, the Manufacturer of Glues, Pastes, Cements, 
and Mucilages, the Compounder of Alloys, the Cook, the Physician, the Druggist, the 
Electrician, the Brewer, the Engineer, the Poundryman, the Machinist, the Potter, the 
Tanner, the Confectioner, the Chiropodist, the Manicure, the Manufacturer of Chem- 
ical Novelties and Toilet Preparations, the Dyer, the Electroplater, the Enameler, the 
Engraver, the Provisioner, the Glass Worker, the Goldbeater, the Watchmaker, the 
Jeweler, the Hat Maker, the Ink Manufacturer, the Optician, the Farmer, the Dairy- 
man, the Paper Maker, the Wood and Metal Worker, the Chandler and Soap Maker, 
the Veterinary Surgeon, and the Technologist Jn general. 

A mine of information, and up-to-date in every respect. A book which will prove of 
value to EVERYONE, as it covers every branch of the Useful Arts. Every home 
needs this book; every office, every factory, every store, every public and private en- 
terprise — EVERYWHERE — shouldj have a copy. 800 pages. Cloth Bound. 
Price $4.00 

WHAT IS SAID OF THIS BOOK: 

"Your Twentieth Century Book of Recipes, Formulas, and Processes duly received. 
I am glad to have a copy of it, and if I could not replace it, money couldn't buy it. It 
Is the best thing of the sort I ever saw." (Signed) M. E. Trux, Sparta, Wis. 
"There are few persons who would not be able to find in the book some single formula 
that would repay several times the cost of the book." — Merchants' Record and Show 
Window. 

" I purchased your book ' Henley's Twentieth Century Book of Recipes, Formulas and 
Processes' about a year ago and it is worth its weight in gold." — Wm. H. Murray, 
Bennington, Vt. 

"THE BOOK WORTH THREE HUNDRED DOLLARS" 

"On close examination of your 'Twentieth Century Receipt Book,' I find it to be a 
very valuable and useful book with the very best of practical information obtainable. 
The price of the book, $4.00, is very small in comparison to the benefits which one can 
obtain from it. I consider the book worth fully three hundred dollars to anyone." 
— Dr. A. C. Spetts, New York. 

"ONE OF THE WORLD'S MOST USEFUL BOOKS" 
" Some time ago, I got one of your ' Twentieth Century Books of Formulas' and have 
made my living from it ever since. I am alone since my husband's death with two 
small children to care for and am trying so hard to support them. I have customers 
who take from me Toilet Articles I put up, following directions given in the book, 
and I have found every one of them to be fine."— Mrs. J. H. McMaken, West Toledo, 
Ohio. - 



34 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



RUBBER 

RUBBER HAND STAMPS AND THE MANIPULATION OF INDIA RUBBER. 

By T. O'Conor Sloane. 

This book gives full details on all points, treating in a concise and simple manner the 
elements of nearly everything it is necessary to understand for a commencement in 
any branch of the India Rubber Manufacture. The making of all kinds of Rubber 
Hand Stamps, Small Articles of India Rubber, U. S. Government Composition, Dating 
Hand Stamps, the Manipulation of Sheet Rubber, Toy Balloons, India Rubber Solu- 
tions, Cements, Blackings, Renovating Varnish, and Treatment for India Rubber 
Shoes, etc.; the Hektograph Stamp Inks, and Miscellaneous Notes, with a Short 
Account of the Discovery, Collection and Manufacture of India Rubber, are set forth 
in a manner designed to be readily understood, the explanations being plain and simple. 
Including a chapter on Rubber Tire Making and Vulcanizing; also a chapter on the 
uses of rubber in Surgery and Dentistry. Third revised and enlarged edition. 175 
Illustrated $1.50 



SAWS 

SAW FILING AND MANAGEMENT OF SAWS. By Robert Grimshaw. 

A practical hand-book on filing, gumming, swaging, hammering, and the brazing of 
band saws, the speed, work, and power to run circular saws, etc. A handy book for 
those who have charge of saws, or for those mechanics who do their own filing, as it deals 
with the proper shape and pitches of saw teeth of all kinds and gives many useful hints 
and rules for gumming, setting, and filing, and is a practical aid to those who use saws 
for any purpose. Complete tables of proper shape, pitch, and saw teeth as well as 
sizes and number of teeth of various saws are included. Fourth edition, revised and 
enlarged. Illustrated. Price $1.50 

SCREW CUTTING 

THREADS AND THREAD-CUTTING. By Colvin and Stable. 

This clears up many of the mysteries of thread-cutting, such as double and triple 
threads, internal threads, catchmg threads, use of hobs, etc. Contains a lot of useful 
hints and several tables. Fourth Edition. Price 35 cents 

STEAM ENGINEERING 

MODERN STEAM ENGINEERING IN THEORY AND PRACTICE. By 

Gardner D. Hiscox. 

This is a complete and practical work issued for Stationary Engineers and Firemen; 
dealing with the care and management of boilers, engines, pumps, superheated steam, 
refrigerating machinery, d5 r namos, motors, elevators, air compressors, and all other 
branches with which the modern engineer must be familiar. Nearly 200 questions with 
their answers on steam and electrical engineering, likely to be asked by the Examin- 
ing Board, are included. 

Among the chapters are: Historical: steam and its properties; appliances for the 
generation of steam; types of boilers; chimney and its work; heat economy of the 
feed water; steam pumps and their work; incrustation and its work; steam above 
atmospheric pressure; flow of steam from nozzles; superheated steam and its work; 
adiabatic expansion of steam; indicator and its work; steam engine proportions; slide 
valve engines and valve motion; Corliss engine and its valve gear; compound engine 
and its theory; triple and multiple expansion engine; steam turbine; refrigeration; 
elevators and their management; cost of power; steam engine troubles; electric 
power and electric plants. 487 pages. 405 engravings. 3d Edition. . . . $3.50 



35 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

1 

AMERICAN STATIONARY ENGINEERING. By W. E. Crane. 

This book begins at the boiler room and takes in the whole power plant. A plain 
talk on every-day work about engines, boilers, and their accessories. It is not intended 
to be scientific or mathematical. All formulas are in simple form so that anyone 
understanding plain arithmetic can readily understand any of them. The author 
has made this the most practical book in print; has given the results of his years of 
experience, and has included about all that has to do with an engine room or a power 
plant. You are not left to guess at a single point. You are shown clearly what to 
expect under the various conditions; how to secure the best results; ways of prevent- 
ing "shut downs" and repairs; in short, all that goes to make up the requirements 
of a good engineer, capable of taking charge of a plant. It's plain enough for practical 
men and yet of value to those high in the profession. 

A partial list of contents is: The boiler room, cleaning boilers, firing, feeding; pumps. 
Inspection and repair; chimneys, sizes and cost; piping; mason work; foundations; 
testing cement; pile driving; engines, slow and high speed; valves; valve setting; 
Corliss engines, setting valves, single and double eccentric; air pumps and condensers; 
different types of condensers; water needed; fining up; pounds; pins not square in 
crosshead or crank; engineers' tools; pistons and piston rings; bearing metal; hard- 
ened copper; drip pipes from cylinder jackets; belts, how made, care of; oils; greases: 
testing lubricants; rules and tables, including steam tables; areas of segments; 
squares and square roots; cubes and cube root; areas and circumferences of circles. 
Notes on: Brick work; explosions; pumps; pump valves; heaters, economizers; 
safety valves; lap, lead, and clearance. Has a complete examination for a license, 
etc., etc. Third edition. 311 pages. 131 Illustrations. Price. . . . $2.50 

ENGINE RUNNER'S CATECHISM. By Robert Grimshaw. 

A practical treatise for the stationary engineer, telling how to erect, adjust, and run 
the principal steam engines in use in the United States. Describing the principal 
features of various special and well-known makes of engines: Temper Cut-off, Shipping 
and Receiving Foundations, Erecting and Starting, Valve Setting, Care and Use, 
Emergencies, Erecting and Adjusting Special Engines. 

The questions asked throughout the catechism are plain and to the point, and the 
answers are given in such simple language as to be readily understood by anyone. All 
the instructions given are complete and up-to-date ; and they are written in a popular 
style, without any technicalities or mathematical formulae. The work is of a handy 
size for the pocket, clearly and well printed, nicely bound, and profusely illustrated. 
To young engineers this catechism will be of great value, especially to those who may 
be preparing to go forward to be examined for certificates of competency; and to 
engineers generally it will be of no little service, as they will find in this volume more 
really practical and useful information than is to be found anywhere else within a like 
compass. 387 pages. Seventh edition. Price $2.00 

HORSE-POWER CHART. 

Shows the horse-power of any stationary engine without calculation. No matter what 
the cylinder diameter of stroke, the steam pressure of cut-off, the revolutions, or 
whether condensing or non-condensing, it's all there. Easy to use, accurate, and 
saves time and calculations. Especially useful to engineers and designers. 60 cents 

STEAM ENGINE CATECHISM. By Robert Grimshaw. 

This unique volume of 413 pages is not only a catechism on the question and answer 
principle, but it Contains formulas and worked-out answers for all the Steam problems 
that appertain to the operation and management of the Steam Engine. Illustrations 
of various valves and valve gear with their principles of operation are given. Thirty- 
four Tables that are indispensable to every engineer and fireman that wishes to be 
progressive and is ambitious to become master of his calling are within its pages. It is 
a most valuable instructor in the service of Steam Engineering. Leading engineers 
have recommended it as a valuable educator for the beginner as well as a reference book 
for the engineer. It is thoroughly indexed for every detail. Every essential question 
on the Steam Engine with its answer is contained in this valuable work. Sixteenth 
edition, Price $2.00 



36 



CATALOGUE OF GOOD, PRACTICAL BOOKS 

STEAM ENGINEER'S ARITHMETIC. By Colvin-Cheney. 

A practical pocket-book for the steam engineer. Shows how to work the problems of 
the engine room and shows "why." Tells how to figure horse-power of engines and 
boilers; area of boilers; has tables of areas and circumferences; steam tables; has a 
dictionary of engineering terms. Puts you on to all of the little kinks in figuring what- 
ever there is to figure around a power plant. Tells you about the heat unit; absolute 
zero: adiabatic expansion; duty of engines; factor of safety; and a thousand and one 
other things; and everything is plain and simple — not the hardest way to figure, but 
the easiest. Second Edition 75 cents 

STEAM ENGINE TROUBLES. By H. Hamkens. 

It is safe to say that no book has ever been published which gives the practical en- 
gineer such valuable and comprehensive information on steam engine design and 
troubles. 

Not only does it describe the troubles the principal parts of steam engines are subject 
to; it contrasts good design with bad, points out the most suitable material for certain 
parts, and the most approved construction of the same; it gives directions for correct- 
ing existing evils by following which breakdowns and costly accidents can be avoided. 
Just look into the nature of the information this book gives on the following sub- 
jects. There are descriptions of cylinders, valves, pistons, frames, pillow blocks and 
other bearings, connecting rods, wristplates, dashpots, reachrods, valve gears, gover- 
nors, piping, throttle and emergency valves, safety stops, fly-wheels, oilers, etc. If 
there is any trouble with these parts, the book gives you the reasons and tells how to 
remedy them. 

The principal considerations in the building of foundations are given with the size, 
area and weight required for the same, also the setting of templets and lining up, and 
a complete account of the erection and "breaking in" of new engines in the language 
of the man on the job. 

Contains special chapters on: I. Cylinders. II. Valves. III. Piping and Separa- 
tors. IV. Throttle and Emergency Valves. V. Pistons. VI. Frames. VII. Bear- 
ings. VIII. Connecting Rods. IX. Hockrods. X. Dashpots. XI. Governors. 
XII. Releasing Gears. XIII. Wristplates and Valve Motions. XIV. Rodends and 
Bonnets. XV. Oilers. XVI. Receivers. XVII. Foundations. XVIII. Erection. 
XIX. Valve-Setting. XX. Operation. 284 pages. 276 illustrations. Price $2.50 

STEAM HEATING AND VENTILATION 

PRACTICAL STEAM, HOT-WATER HEATING AND VENTILATION. By 
A. G. King. 

This book is the standard and latest work published on the subject and has been pre- 
pared for the use of all engaged in the business of steam, hot-water heating, and ventila- 
tion. It is an original and exhaustive work. Tells how to get heating contracts, how 
to install heating and ventilating apparatus, the best business methods to be used, 
with "Tricks of the Trade" for shop use. Rules and data for estimating radiation 
and cost and such tables and information as make it an indispensable work for every- 
one interested in steam, hot- water heating, and ventilation. It describes all the principal 
systems of steam, hot-water, vacuum, vapor, and vacuum-vapor heating, together 
with the new accelerated systems of hot-water circulation, including chapters on 
up-to-date methods of ventilation and the fan or blower system of heating and ventila- 
tion. Containing chapters on: I. Introduction. II. Heat. III. Evolution of 
artificial heating apparatus. IV. Boiler surface and settings. V. The chimney flue. 
VI. Pipe and fittings. VII. Valves, various kinds. VIII." Forms of radiating 
surfaces. IX. Locating of radiating surfaces. X. Estimating radiation. XI. Steam- 
heating apparatus. XII. Exhaust-steam heating. XIII. Hot-water heating. XIV. 
Pressure systems of hot-water work. XV. Hot- water appliances. XVI. Greenhouse 
heating. XVII. Vacuum vapor and vacuum exhaust heating. XVIII. Miscella- 
neous heating. XIX. Radiator and pipe connections. XX. Ventilation. XXI. 
Mechanical ventilation and hot-blast heating. XXII. Steam appliances. XXIII. 
District heating. XXIV. Pipe and boiler covering. XXV. Temperature regulation 
and heat control. XXVI. Business methods. XXVII. Miscellaneous. XXVIII. 
Rules, tables, and useful information. 402 pages. 300 detailed engravings. Third 
Edition — Revised. Price . .. , f ,,,,,,, , $3.5$ 

37 



CATALOGUE OF GOOD, PRACTICAL BOOKS 
< 

500 PLAIN ANSWERS TO DIRECT QUESTIONS ON STEAM, HOT-WATER, 
VAPOR AND VACUUM HEATING PRACTICE. By Alfred G. King. 
This work, just off the press, is arranged in question and answer form ; it is intended as 
a guide and text-book for the younger, inexperienced fitter and as a reference book for 
all fitters. This book tells "how" and also tells "why." No work of its kind has 
ever been published. It answers all the questions regarding each method or system 
that would be asked by the steam fitter or heating contractor, and may be used as a 
text or reference book, and for examination questions by Trade Schools or Steam 
Fitters' Associations. Rules, data, tables and descriptive methods are given, to- 
gether with much other detailed information of daily practical use to those engaged in 
or interested in the various methods of heating. Valuable to those preparing for 
examinations. Answers every question asked relating to modern Steam, Hot-Water, 
Vapor and Vacuum Heating. Among the contents are: The Theory and Laws of 
Heat. Methods of Heating. Chimneys and Flues. Boilers for Heating. Boiler 
Trimmings and Settings. Radiation. Steam Heating. Boiler, Radiator and Pipe 
Connections for Steam Heating. Hot Water Heating. The Two-Pipe Gravity 
System of Hot Water Heating. The Circuit System of Hot Water Heating. The 
Overhead System of Hot Water Heating. Boiler, Radiator and Pipe Connections for 
Gravity Systems of Hot Water Heating. Accelerated Hot Water Heating. Ex- 
pansion Tank Connections. Domestic Hot Water Heating. Valves and Air Valves. 
Vacuum Vapor and Vacuo- Vapor Heating. Mechanical Systems of Vacuum Heating. 
Non-Mechanical Vacuum Systems. Vapor Systems. Atmospheric and Modulating 
Systems. Heating Greenhouses. Information, Rules and Tables. 214 pages, 127 
illustrations. Octavo. Cloth. Price , , . $2.00 

STEEL 

STEEL: ITS SELECTION, ANNEALING, HARDENING, AND TEMPERING. 
By E. R. Markham. 

This book tells how to select, and how to work, temper, harden, and anneal steel for 
everything on earth. It doesn't tell how to temper one class of tools and then leave 
the treatment of another kind of tool to your imagination and judgment, but it gives 
careful instructions for every detail of every tool, whether it be a tap, a reamer or just 
a screw-driver. It tells about the tempering of small watch springs, the hardening of 
cutlery, and the annealing of dies. In fact, there isn't a thing that a steel worker 
would want to know that isn't included. It is the standard book on selecting, harden- 
ing, and tempering all grades of steel. Among the chapter headings might be mentioned 
the following subjects: Introduction; the workman; steel; methods of heating; 
heating tool steel; forging; annealing; hardening baths; baths for hardening; harden- 
ing steel; drawing the temper after hardening; examples of hardening; pack harden- 
ing; case hardening; spring tempering; making tools of machine steel; special steels; 
steel for various tools, causes of trouble; high speed steels, etc. 400 pages. Very 
fully illustrated. Fourth Edition. Price $3.00 

HARDENING, TEMPERING, ANNEALING, AND FORGING OF STEEL. 
INCLUDING HEAT TREATMENT OF MODERN ALLOY STEELS. By 

J. V. WOODWORTH. 

A new work treating in a clear, concise manner all modern processes for the heating, 
annealing, forging, welding, hardening, and tempering of high and low grade steel, 
making it a book of great practical value to the metal-working mechanic in general, 
with special directions for the successful hardening and tempering of all steel tools 
used in the arts, including milling cutters, taps, thread dies, reamers, both solid and 
shell, hollow mills, punches and dies, and all kinds of sheet metal working tools, shear 
blades, saws, fine cutlery, and metal cutting tools of all description, as well as for all 
implements of steel both large and small. In this work the simplest and most satis- 
factory hardening and tempering processes are given. 

The uses to which the leading brands of steel may be adapted are concisely presented, 
and their treatment for working under different conditions explained, also the special 
methods for the hardening and tempering of special brands. 

A chapter devoted to the different processes for case-hardening is also included, and 
special reference made to the adaptation of machinery steel for tools of various kinds. 
5th Edition, 321 pages. 201 illustrations. /Price $3.00 



38 



CATALOGUE OF GOOD, PRACTICAL BOOKS 



TRACTORS 

MODERN GAS TRACTOR: ITS CONSTRUCTION, UTILITY, OPERATION 
AND REPAIR. By Victor W. Page. 

An enlarged and revised edition that treats exclusively on the design and construction 
of farm tractors and tractor power plants, and gives complete instructions on their 
care, operation and repair. All types and sizes of gasoline, kerosene and oil tractors 
are described, and every phase of traction engineering practice fully covered. In- 
valuable to all desiring reliable information on gas motor propelled traction engines 
and their use. All new 1921 types of tractors are described and complete instructions 
are given for their use on the farm. The chapter on engine repairing has been greatly 
enlarged and complete and detailed instructions are now given for repairing weh- 
known and widely used tractor power plants, numerous new forms of which are 
described. Valuable information compiled by Government experts on laying out 
fields for tractor plowing and numerous practical suggestions for hitches so all types 
of agricultural machinery can be operated by tractors, are outlined. The chapter 
on tractor construction and upkeep has been more than doubled in size. Over 100 
new illustrations have been added and the book greatly enlarged. Full instructions 
are now given for using kerosene and distillate as fuel. The 1921 edition is 50 per 
cent larger than the second edition and is more than ever the acknowledged authority 
on farm tractors and their many uses. 5M x 7H inches. Cloth, nearly 700 pages, 
and about 300 illustrations, 3 folding plates. Price $3.00 

WELDING 

MODERN WELDING METHODS. By Victor W. Pag& 

One of the most instructive books on all methods of joining metals yet published for 
the mechanic and practical man. It considers in detail oxy-acetylene welding, the 
Thermit process and all classes of electric arc and resistance welding. It shows all 
the apparatus needed and how to use it. It considers the production of welding gases, 
construction and operation of welding and cutting torches of all kinds. It details 
the latest approved methods of preparing work for welding. All forms of gas and 
electric welding machines are described and complete instructions are given for 
installing electric spot and butt welders. Cost data are given and all methods of 
doing the work economically are described. It includes instructions for forge and 
dip brazing and manufacture of hard solders and spelters. It shows and explains 
soft soldering processes and tells how to make solders for any use. Complete instruc- 
tions are given for soldering aluminum and authoritative formulas for aluminum solders 
are included. 292 pages. 200 illustrations. 1921 edition. Price . . $3.00 

AUTOMOBILE WELDING WITH THE OXY-ACETYLENE FLAME. By 

M. Keith Dunham. 

Explains in a simple manner apparatus to be used, its care, and how to construct 
necessary shop equipment. Proceeds then to the actual welding of all automobile 
parts, in a manner understandable by everyone. Gives principles never to be for- 
gotten. This book is of utmost value, since the perplexing problems arising when 
metal is heated to a melting point are fully explained and the proper methods to 
overcome them shown. 167 pages. Fully illustrated. Price $1.50 



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